Snakes, an order (Ophidia) in the class of Reptiles. They may be characterized as very elongated reptiles without limbs (unless with tiny vestiges of posterior limbs), without eyelids and external ear openings, with the teeth anchylosed to the supporting bones, a bifid slender tongue which is telescoped into its basal half, and with a transverse vent. These characters apply to all snakes, although none are peculiar to them. The ' The curious but apparently well-attested fact of the occurrence in England, near Poole, in June 1851, of a male bird of this species (Zoologist, pp. 3601, 3654) has been overlooked by several writers who profess to mention all cases of a similar character.
vast majority of snakes are further characterized by having the right and left halves of the under-jaws connected by an elastic band; a median, longitudinal furrow in the skin below and behind the chin; the whole palatal apparatus is but loosely connected with the skull, nowhere articulating with it. The quadrate is indirectly articulated with the skull, first by the horizontal, movable squamosal, secondly by the columella auris. The quadrato-mandibular joint is placed in a level far behind the occiput.
More detail concerning skull, scales and teeth will be found in the diagnostic descriptions of the various families (vide infra); for further anatomical information the reader is referred to the article Reptiles (Anatomy). The snakes are the most highly specialized branch of the Sauria or Squamata, i.e. of scaly reptiles with movable quadrate bones; with a transverse vent, near the posterior lateral corners of which open the eversible, paired copulatory organs. In the article Lizard attention is drawn to the many characters which make it difficult, if not impossible, to give diagnoses applicable to all lizards and all snakes. Both these groups seem to have reached their climax but recently, while the tortoises, crocodiles and sphenodon are on the descending scale, mere remnants of formerly much more numerous and cosmopolitan development.
The number of recent species of snakes is about 1600. The order is practically cosmopolitan, with the exception of New Zealand and certain absolutely isolated oceanic islands, like the Hawaiian islands and the Azores. The N. limit approaches that of the permanently frozen subsoil, going into the arctic circle in Scandinavia, elsewhere sinking to about 54° N.; in the S. hemisphere the 45th parallel may indicate their limit. The number of species and individuals steadily decreases in the cooler temperate zones, whilst it reaches its maximum in the tropics. Every kind of terrain is tenanted, from dense, moist and hot forests at the level of the sea to arid deserts, high plateaus and mountains. In accordance with this general distribution snakes show a great amount of differentiation with regard to their mode of life and general organization; and from the appearance alone of a snake a safe conclusion can be drawn as to its habits.
Dr A. Gunther characterizes the chief categories as follows: - (I) Burrowing snakes, which live under ground and but rarely appear on the surface. They have a cylindrical rigid body, covered with generally smooth and polished scales; a short strong tail; a short rounded or pointed head with narrow mouth; teeth few in number; small or rudimentary eyes; no abdominal scutes or only narrow ones. They feed chiefly on invertebrate animals, and none are poisonous. (2) Ground snakes rarely ascending bushes or entering water. Their body is cylindrical, flexible in every part, covered with smooth or keeled scales, and provided with broad ventral and subcaudal scutes. The non-poisonous kinds of ground snakes are the typical and least specialized snakes, and more numerous than any of the other kinds. They feed chiefly on terrestrial vertebrates. The majority are non-poisonous; but the majority of poisonous snakes must be referred to this category. (3) Tree snakes, which are able to climb bushes or trees with facility or pass even the greater part of their existence on trees. Their body is generally compressed and slender; their broad ventral scutes are often carinate on the sides. Those kinds which have a less elongate and cylindrical body possess a distinctly prehensile tail. The eye is generally large. Their coloration consists often of bright hues, and sometimes resembles that of their surroundings. They feed on animals which likewise lead an arboreal life, rarely on eggs. Poisonous as well as innocuous snakes are represented in this category. (4) Freshwater snakes, living in or frequenting fresh waters; they are excellent swimmers and divers. The nostrils are placed on the top of the snout and can be closed whilst the animal is under water. Their body is covered with small scales and the ventral scutes are mostly narrow; the tail tapering; head flat, rather short; and the eyes of small size. They feed on fish, frogs and other aquatic animals, and are innocuous and viviparous. (5) Sea snakes are distinguished by the compressed, rudder-shaped tail. They are unable to move on land, feed on fishes, are viviparous and poisonous.
The majority of snakes are active during the day, their energy increasing with the increasing temperature; whilst some delight in the moist sweltering heat of dense tropical vegetation, others expose themselves to the fiercest rays of the midday sun. Not a few, however, lead a nocturnal life, and many of them have, accordingly, their pupil contracted into a vertical or more rarely a horizontal slit. Those which inhabit temperate latitudes hibernate. Snakes are the most stationary of all vertebrates; as long as a locality affords them food and shelter they have no inducement to change it. Their dispersal, therefore, must have been extremely slow and gradual. Although able to move a FIG. I. - Diagram of Natural Locomotion of a Snake.
with rapidity, they do not keep in motion for any length of time. Their organs of locomotion are the ribs, the number of which is very great, nearly corresponding to that of the vertebrae of the trunk. They can adapt their motions to every variation of the ground over which they move, yet all varieties of snake locomotion are founded on the following simple process. When a part of the body has found some projection of the ground which affords it a point of support, the ribs are drawn more closely together, on alternate sides, thereby producing alternate bends of the body. The hinder portion of the body being drawn of ter, some part of it (c) finds another support on the rough ground or a projection; and, the anterior bends being stretched in a straight line, the front part of the body is propelled (from a to d) in consequence. During this peculiar locomotion the numerous broad shields of the belly are of great advantage, as by means of their free edges the snake is enabled to catch and use as points of support the slightest projections of the ground. A pair of ribs corresponds to each of these ventral shields. Snakes are not able to move over a perfectly smooth surface. The conventional representation of the progress of a snake, in which its undulating body is figured as resting by a series of lower bends on the ground whilst the alternate bends are FIG. 2. - Diagram of Conventional Idea of a Snake's Locomotion.
raised above it, is an impossible attitude, nor do snakes ever climb trees in spiral fashion, the classical artistic mode of representation. Also the notion that snakes when attacking are able to jump off the ground is quite erroneous; when they strike an object, they dart the fore part of their body, which was retracted in several bends, forwards in a straight line. And sometimes very active snakes, like the cobra, advance simultaneously with the remainder of the body, which, however, glides in the ordinary fashion over the ground; but no snake is able to impart such an impetus to the whole of its body as to lose its contact with the ground. Some snakes can raise the anterior part of their body and even move in this attitude, but it is only about the anterior fourth or third of the total length which can be thus erected.
With very few exceptions, the integuments form imbricate scalelike folds arranged with the greatest regularity; they are small and pluriserial on the upper parts of the body and tail, large and uniserial on the abdomen, and generally biserial on the lower side of the tail. The folds can be stretched out, so that the skin is capable of a great degree of distension. The scales are sometimes rounded behind, but generally rhombic in shape and more or less elongate; they may be quite smooth or provided with a longitudinal ridge or keel in the middle line. The integuments of the head are divided into non-imbricate shields or plates, symmetrically arranged, but not corresponding in size or shape with the underlying cranial bones or having any relation to them. The form and number of the scales and scutes, and the shape and arrangement of the head-shields, are of great value in distinguishing the genera and species, and it will therefore be useful to explain in the accompanying woodcut (fig. 3) the terms by which these parts are designated: The skin does not form eyelids; but the epidermis passes over the eye, forming a transparent disk, concave like the glass of a watch, behind which the eye moves. It is the first part which is cast off when the snake sheds its skin; this is done several times in the year, and the epidermis comes off in a single piece, being, from the mouth towards the tail, turned inside out during the process.
The tongue in snakes is narrow, almost worm-like, generally of a black colour and forked, that is, it terminates in front in two extremely fine filaments. It is often exserted with a rapid motion, sometimes with the object of feeling some object, sometimes under the influence of anger or fear.
Snakes possess teeth in the maxillaries, mandibles, palatine and pterygoid bones, sometimes also in the intermaxillary; they may be absent in one or the ether of the bones mentioned. In the innocuous snakes the teeth are simple and uniform in structure, thin, sharp like needles, and bent backwards; their function consists merely in seizing and holding the prey. In some all the teeth are nearly of the same size; others possess in front of the jaws (Lycodonts) or behind in the maxillaries (Diacrasterians) a tooth more or less con spicuously larger than the rest; whilst others again are distinguished by this larger posterior tooth being grooved along its outer face. The snakes with this grooved kind of tooth have been named Opisthoglyphi, and also Suspecti, because their saliva is more or less poisonous. In the true poisonous snakes the maxillary dentition has undergone a special modification. The so-called colubrine venomous snakes, which retain in a great measure an external resemblance to the innocuous snakes, have the maxillary bone not at all, or but little, shortened, armed in front with a fixed, erect fang, which is provided with a deep groove or canal for the conveyance of the poison, the fluid being secreted by a special poison-gland. One or more small ordinary teeth may be placed at some distance behind this poison-fang. In the other venomous snakes (viperines and crotalines) the maxillary bone is very short, and is armed with a single very long curved fang with a canal and aperture at each end. Although firmly anchylosed to the bone, the tooth, which when at rest is laid backwards, is erectile, - the bone itself being mobile and rotated round its transverse axis. One or more reserve teeth, in various stages of development, lie between the folds of the gum and are ready to take the place of the one in function whenever it is lost by accident, or shed.
The poison is secreted in modified upper labial glands, or in a pair of large glands which are the homologues of the parotid salivary glands of other animals. For a detailed account see West, J. Linn. Soc. xxv. (1895), p. 419; xxvi. (1898), p. 517; and xxviii. (1900). A duct leads to the furrow or canal of the tooth. The Elapinae have comparatively short fangs, while those of the vipers, especially the crotaline snakes, are much longer, sometimes nearly an inch in length. The Viperidae alone have "erectile" fangs. The mechanism is explained by the diagrams (fig. 4). The poison-bag lies on the side of the head between the eye and the mandibular joint and is held in position by strong ligaments which are attached to this joint and to the maxilla so that the act of opening the jaws and concomitant erection of the fangs automatically squeezes the poison out of the glands.
r
Snakes are carnivorous, and as a rule take living prey only; a few feed habitually or occasionally on eggs. Many swallow FIG. 3. - Head-shields (Ptyas korros). r, Rostral.
f, Posterior frontal.
f ', Anterior frontal.
v, Vertical.
s, Supraciliary or supraocular.
o, Occipital. n, n', Nasals.
1, Loreal.
a, Anterior ocular or orbital, or praeorbital or anteocular.
p, Postoculars.
u, u, Upper labials.
t, t, Temporals. m, Mental.
, *, Lower labials. c, c, Chin-shields.
of a Snake their victim alive; others first kill it by smothering it between the coils of their body (constriction). The effects of a bite by a poisonous snake upon a small mammal or bird are almost instantaneous, preventing its escape; and the snake swallows its victim at its leisure, sometimes hours after it has been killed. The prey is always swallowed entire, and, as its girth generally much exceeds that of the snake, the progress of deglutition is very laborious and slow. Opening their jaws to their fullest extent, they seize the animal generally by the head, and pushing alternately the right and left sides of the jaws forward, they press the body through their elastic gullet into the stomach, its outlines being visible for some time through the distended walls of the abdomen. Digestion is quick and much accelerated by the quantity of saliva which is secreted during the progress of deglutition, and in venomous snakes probably also by the chemical action of the poison. The primary function of the poisonapparatus is to serve as the means of procuring their food, but From Cambridge Natural History, vol. viii., "Amphibia and Reptiles," by permission of Macmillan & Co., Ltd.
FIG. 4. - Poison Apparatus of Rattlesnake. Upper figures: diagrams of skull with fangs at rest. Lower figures: same, with fangs protruded. G, prefrontal; M, maxilla; J, poison-fang; Tr, transpalatine; Pt, pterygoid; p, palatine; Q, quadrate; Sq, squamosal; Pm, premaxilla; T.a, articular; Pe and Di, muscles.
it also serves for defence. Only very few poisonous snakes (like Naja elaps) are known to resent the approach of man so much as to follow him on his retreat and to attack him. Others are much less inclined to avoid collision with man than innocuous kinds. They have thus become one of the greatest scourges to mankind, and Sir J. Fayrer has demonstrated that in India alone annually some 20,000 human beings perish from snake-bites. Therefore it will not be out of place to add here a chapter on snake poison and on the best means (ineffectual though they be in numerous cases) of counteracting its deleterious effects. An excellent account of the nature and of the effect of the venom of snakes, by Charles J. Martin, is in Allbutt's System of Medicine. The following condensed account has been abstracted from it.
The poison is a clear, pale-yellow fluid which reacts acid, and contains about 30% of solids, but this varies according to the state of concentration. Most venoms are tasteless, but cobra poison is said to be disagreeably bitter. Dried venom keeps indefinitely, and dissolves readily in water. It keeps also in glycerine. It contains albuminous bodies in solution, and is in fact a pure solution of two or more poisonous proteids, which are the active agents, with a small quantity of an organic acid or colouring matter. The venom is destroyed by reagents which precipitate prdteids in an insoluble form, or which destroy them, e.g. silver nitrate or permanganate of potash. Hypochlorites have the same effect. But carbolic acid and caustic potash destroy it only after a day or two, consequently they are not a remedy.
The venom is generally introduced into the subcutaneous tissue, whence it reaches the general circulation by absorption through the lymph and blood-vessels. When introduced directly into a vein, the effects are instantaneous. It is absorbed by the conjunctiva, but, excepting cobra poison, not by the mouth or alimentary canal, provided there be no hollow teeth and no abrasions. The venom of the various kinds of snakes acts differently.
The Symptoms of Cobra Poison. - Burning pain, followed by sleepiness and weakness in the legs after half an hour. Then profuse salivation, paralysis of the tongue and larynx, and inability to speak. Vomiting, incapacity of movement. The patient seems to be conscious. Breathing becoming difficult. The heart's action is quickened. The pupil remains contracted and reacts to light. At length breathing ceases, with or without convulsions, and the heart slowly stops. Should the patient survive, he returns rapidly to complete health.
The painful wound is speedily discoloured and swollen. Constitutional symptoms appear as a rule in less than fifteen minutes: prostration, staggering, cold sweats, vomiting, feeble and quick pulse, dilatation of the pupil, and slight mental disturbance. In this state the patient may die in about twelve hours. If he recovers from the depression, the local symptoms begin to play a much more important part than in cobra-poisoning: great swelling and discoloration extending up the limb and trunk, rise of temperature and repeated syncope, and laboured respiration. Death may occur in this stage. The local haemorrhagic extravasation frequently suppurates, or becomes gangrenous, and from this the patient may die even weeks afterwards. Recovery is sudden, and within a few hours the patient becomes bright and intelligent.
Local burning pain; the bitten limb soon swells and is discoloured. Great prostration, vomiting and cold, clammy perspiration follow within one to three hours. Pulse very feeble, with slight difficulty in breathing, and restlessness. In severe cases the pulse may become imperceptible, the extremities may become cold, and the patient may pass into coma. In from twelve to twenty-four hours these severe constitutional symptoms usually pass off, but in the meantime the swelling and discoloration have spread enormously. Within a few days recovery usually occurs somewhat suddenly, but death may occur from the severe depression, or from the secondary effects of suppuration.
The symptoms of the bite from the Daboia or Vipera russeli resemble the effects of rattlesnake poison, but sanious discharges from the rectum, &c., are an additional and prominent feature. The recovering patient suffers from haemorrhagic extravasations in various organs, besides from the lungs, nose, mouth and bowels. Kidney haemorrhage and albuminuria is a constant symptom. The pupil is always dilated and insensitive to light.
Pain and local swelling. The first constitutional symptoms appear in fifteen minutes to two hours. First faintness and irresistible desire to sleep. Then alarming prostration and vomiting. Pulse extremely feeble and thread-like, and uncountable. The limbs are cold and the skin is blanched. Respiration becomes shallow with the increasing coma. Sensation is blunted. The pupil is widely dilated and insensible to light. There is sometimes passing of blood. If the patient survives the coma, recovery is complete and as a rule rapid, without secondary symptoms.
The Australian venom and that of all viperine snakes, perhaps also that of the cobra, if introduced rapidly into the circulation, occasions extensive intravascular clotting. If the venom is slowly absorbed, the blood loses its coagulability, owing to the breaking down of the red blood-corpuscles, most so with vipers, less with Australian snakes, least so with the cobra. The cobra venom is supposed to extinguish the functions of the various nerve-centres of the cerebro-spinal system, the paralysation extending from below upwards, and it has a special affinity for the respiratory centre. The toxicity or relative strength of the cobra venom has been calculated to be sixteen times that of the European viper. Snakes can poison each other, even those of the same kind.
Apply a ligature above, not on the top of, the situation of the bite, twist the string tightly with a stick. Then make a free incision into the wound. Sucking out is dangerous! Then bandage the limb downwards, progressing towards the wound; repeat this several times. Do not keep the ligature longer than half an hour. Then let the circulation return, and apply the ligature again. In any case do not keep the ligature on for more than an hour for fear of gangrene. Direct application into the widened wound of calcium hypochlorite, i.e. bleaching powder, is very good, or of a I % solution of permanganate of potash, or Condy's fluid. Vigorous cauterization with nitrate of silver, driving the stick into the widened wound, is also good, and it is a remedy which one can carry in the pocket. Quick amputation of the finger is the best remedy of all if a large snake has bitten it.
The administration of enormous doses of alcohol is to be condemned strongly. Small, stimulating doses, and repeated, are good, but stimulation can be more effectively produced by ammonia or strychnine. Hypodermic injection of strychnine, in some cases as much as one to two grains (but not into a vein!), has in some cases had good results; but injection of ammonia, instead of doing any good, has disastrous sloughing results. There is only one fairly reliable treatment, that by serum therapeutics, the injection of considerable quantities of serum of animals which have e?
been partially immunized by repeated doses of [that particular] snake-venom. Unfortunately this treatment will not often be available. Several manimals and birds are supposed to be immune by nature against snake-venom. Some more or less immune creatures are the mongoose, the hedgehog and the pig, the secretary-bird, the honey buzzard, the stork and probably other snake-eaters.
Snakes are oviparous; they deposit from ten to eighty eggs of an ellipsoid shape, covered with a soft leathery shell, in places where they are exposed to and hatched by moist heat. The parents pay no further attention to them, except the pythons, which incubate their eggs by coiling their body over them, and fiercely defend them. In some families, as many freshwater snakes, the sea snakes, Viperinae and Crotalinae, the eggs are retained in the oviduct until the embryo is fully developed. These snakes bring forth living young.
The classification of snakes has undergone many vicissitudes. J. Muller (Zeitschr. f. Physiol., 1831, p. 265) divided them into Ophidia macrostomata and 0. microstomata. A. M. C.
Dumeril (Catal. methodique, Mus. d'Hist. Nat., Paris, 1851,1851, p. 199) distinguished between Opoterodonta, Aglyphodonta, Proteroglypha and Solenoglypha. H. Stannius (Zootomie d. Amphib., 1856) made a further improvement by combination of the principles used by his predecessors, and he divided the Angiostomata or narrow-mouthed snakes into Tortricina, Typhlopina and Uropeltacea; the Eurystomata into Iobola or poisonous, and Asinea or innocuous snakes. Meanwhile J. E. Gray (Cat. Snakes, Brit. Mus., 1849) had distinguished only between Viperina and Colubrinia. A. Gunther (Cat. Colubrine Snakes, Brit. Mus., 1858; "Reptiles of British India," Ray Soc., 1864; article Snakes, Ency. Brit., 9th ed.) recognized at last four sub-orders: - Hopoterodontes, Colubriformes, Colubriformes venenosi, Viperiformes; the most serious drawback being the merging of the Peropoda in the non-poisonous Colubriformes. E. D. Cope (Proc. Ac. Philad., 1864, p. 230) resorted to the modifications of the squamosal, ectoand endopterygoid bones, the condition of the vestigial limbs, and the teeth:- Scolecophidia (Typhlopidae), Catodonta (Glauconiidae), Tortricina (Ilysiidae and' Uropeltidae), Asinea, Proteroglypha and Solenoglypha. He adhered to this arrangement in his last comprehensive work (Crocodilians, Lizards and Snakes of North America, 1898, Smithsonian Inst., 1900), but combined the Asinea and Proteroglypha as Colubroidea, subdividing these into Peropoda, Aglyphodonta, Glyphodonta, Proteroglypha and Platycerca (Hydrophinae). In his last work he used, with doubtful success, the variations of the penes and the lungs as additional characters, chiefly for the grouping of the great mass of the Colubroid snakes. G. A. Boulenger (Cat. Snakes, Brit. Mus., 1893-1896) accepted Cope's principles, and mainly by .combining the Asinea of Stannius and Cope with the Proteroglypha as Colubridae - wherein he was followed by Cope, as mentioned above - and separating therefrom the Peropoda or Boidae, he has produced a logically-conceived system, by far the best hitherto proposed. It is followed in the present article.
Boulenger's phylogenetic system stands as follows: Viperidae Uropeltidae C. Opisthoglypha C. Proteroglypha Amblycephalidae mandible to the aglyphous or innocuous Colubridae, whence further differentiation in three new lines has taken place, - (i) the harmless Amblycephalidae as a side-issue, (2) the very poisonous proteroglyphous Elapidae, (3) the moderately or incipiently poisonous Opisthoglypha, out of some of which seem to have arisen the venomous Viperidae.
I. No ectopterygoidpterygoid not extending to quadrate; no supratemporal or squamosal; prefrontal forming a suture with nasal; coronoid present; vestiges of pelvis present.
Maxillary vertical, loosely attached, toothed; mandible toothless; a single pair of pelvis bones: Typhlopidae. Maxillary bordering the mouth, forming sutures with the premaxillary, prefrontal and frontal, toothless; lower jaw toothed; pubis and ischium present, the latter forming a symphysis: Glauconiidae. II. Ectopterygoid present; upper and lower jaws toothed.
A. Coronoid present, prefrontal in contact with nasal.
i. Vestiges of hind-limbs; supratemporal present.
Squamosal large, suspending the quadrate: Boidae. Squamosal small, intercalated in the cranial wall: Ilysiidae. 2. No vestiges of limbs. squamosal absent: Uropeltidae. B. Coronoid absent; squamosal present.
1. Maxillary horizontal; pterygoid reaching quadrate or mandible.
Prefrontal in contact with nasal: Xenopeltidae. Prefrontal not in contact with nasal: Colubridae. 2. Maxillary horizontal; pterygoid not reaching quadrate or mandible: Amblycephalidae. 3. Maxillary vertically erectile, perpendicularly to ectoptery goid, and reaching quadrate or mandible: Viperidae. For ordinary practical purposes this synopsis is useless, most of the anatomical characters being visible only in the macerated skull. The following characterization of the families is based upon more accessible features.
Eyes vestigial or hidden; lower jaw toothless; without enlarged ventral scales: Typhlopidae. Eyes vestigial; teeth restricted to the lower jaw; without en- larged ventral scales: Glauconiidae. Eyes very small; head not distinct; teeth in the upper and lower jaws; ventral scales scarcely enlarged; tail extremely short, ending obtusely and covered with peculiar scales: Uropettidae. Eyes functional, free, with vestiges of the hind-limbs appearing as claw-like spurs on each side of the vent.
Ventral scales scarcely enlarged: Ilysiidae. Ventral scales transversely enlarged: Boidae. Eyes free; with a pair of poison-fangs in the front part of the mouth, carried by the otherwise toothless, much shortened, and vertically erectile maxillaries; ventral scales transversely enlarged: Viperidae. All the remaining snakes combine the following characters. the maxillaries are typically horizontal, not separately movable, with a series of teeth. The mandible is toothed but has no coronoid bone. There are no vestiges of limbs or of their girdles. The eyes are free.
Dentary movably attached to the tip of the articular bone of the mandible. Skin beautifully iridescent: Xenopeltidae. Without a mental groove; the ends of the pterygoids are free, not reaching the quadrate. Head thick and very distinct: Amblycephalidae. With a median longitudinal groove between the shields of the skin: Colubridae. Family 1. TYPHLoPIDAE. - Burrowing snakes, mostly small, which have the body covered with smooth, shiny, uniform cycloid scales The teeth are restricted to the small maxillary bones. The quadrates slant obliquely forward and are attached directly to the proOtics, owing to the absence of squamosals. The prefrontals are in lateral contact with the nasals. The vestiges of the pelvis are reduced to a single bone on each side, and there are no traces of limbs. The eyes are hidden by shields of the skin. The mouth is very narrow, and the halves of the under-jaw are not distensible. About 100 species of these rather archaic snakes are known; in adaptation to their burrowing life and worm and insect diet, they have undergone degradation. The tail is mostly very short and sometimes ends in a horny spine. They are widely distributed in all tropical and subtropical countries, even in such solitary places as Christmas Island, but they do not occur in New Zealand. The chief genus is Typhlops, FIG. 5. - Typhlops bothriorhynchus, from India, natural size.
Ilysiidae Xenopeltidae Colubridae Aglypha Typhlopidae Boidae Glauconiidae 'This means that the Boidae retain most primitive characters. Likewise primitive, but in various respects degraded, mainly owing to burrowing habits, are the Typhlopidae with the Ilysiidae, and Uropeltidae as a terminal branch, and on the other hand the Glauconiidae. The solitary Xenopeltis is in several ways intermediate between Boidae and Ilysiidae. The rest of the snakes are supposed to have started from some primitive, nondegenerate, therefore boa-like group, leading by loss of the vestiges of the hind-limbs and loss of the coronoid bone of the of which, for instance, T. braminus ranges from southern Asia, the islands of the Indian Ocean and the Malay Islands to southern Africa.
Family 2. GLAuc0NIIDAE. - Burrowing like the Typhlopidae, which they much resemble externally, but the maxillaries retain their normal position and are toothless, teeth being restricted to the lower jaw, which is short, stout, and not distensible. The pelvic girdle and the hind-limbs show the least reduction found in any recent snakes, ilia, pubes and ischia being still distinguishable, the last even retaining their symphysis, and there are small vestiges of the femurs. About 30 species, mostly of the genus Glauconia, in south-western Asia, Africa, Madagascar, the Antilles and both Americas, G. dulcis ranging northwards into Texas, G. hunsilis into California.
Family 3. Ilysiidae. - Mostly burrowing. The scales of the long, cylindrical body are smooth and small, scarcely enlarged on the ventral side. The tail is extremely short and blunt. The head is very small and not distinct from the neck, a usual feature in burrowing snakes and lizards. The gape of the mouth is narrow. The quadrate bones are short and stand rather vertically. The squamosals form part of the cranial wall, being firmly wedged in between the quadrate, prootic and occipital bones. Vestiges of the pelvis and hind-limbs are small, but they terminate in claw-like spurs which protrude FIG. 6. - Three between the scales on either side of the vent, Views of Head of as in the Boidae. The small eyes are some- T y p h l o p s bra- times covered by transparent shields. About minus (India)half-a-dozen species only are known in South magnified. ' America, Ceylon, the Malay Islands and Indo China. They are viviparous like the Typhlopidae, upon which they feed besides worms and insects. Ilysia s. Tortrix scytale, one of the "coral-snakes" of tropical South America, is beautiful coral-red with black rings, grows to nearly a yard in length, and is said sometimes to be worn as a necklace by native ladies.
Family 4. Uropeltidae (Rhinophidae). - Burrowing snakes of Ceylon and southern India, with a very short tail, which ends in a peculiar, often obliquely truncated, shield, hence the name. The eyes are very small. The scales of the body are smooth and are but little larger on the belly. The coloration is mostly beautiful, black and red. The Uropeltidae are in various respects intermediate between the two last and the next family. The quadrates are directly attached to the skull, the squamosals being absent. Teeth are carried in both jaws. There are no vestiges of hind-limbs or of the pelvis.
These tail-shielded snakes, of which about 40 species are known, are viviparous and burrow in the ground, preferring damp mountainforests. Uropeltis grandis, the only species of the type-genus, is confined to Ceylon; about 18 in. in length, it is blackish above, yellow below, often with small spots on the upper and the under surface. Rhinophis sanguineus lives in southern India; it is black above with a bluish gloss, the belly is bright red with black spots, like the convex tail-shield.
Family 5. BoIDAE. - Typical, often very large, snakes, which have vestiges of pelvis and hind-limbs, the latter appearing as claw-like spurs on each side of the vent. The scales of the upper surface are usually small and smooth, while those of the belly form one broad series. The quadrate is carried by the horizontally-elongated squamosal, which rests loosely upon the skull. The prefrontals are in contact with the nasals. Sharp, recurved teeth are carried by the mandibles, the pterygoids, palatines, maxillaries, and in the Pythoninae by the premaxillaries also. The Boidae comprise some 60 species, which have been grouped into many fancy genera. The range of the family extends over all the tropical and subtropical countries, including islands, except New Zealand.
Sub-family 1. Pythoninae. - With a pair of supraorbital bones between the prefrontal, frontal and postfrontal bones. The premaxilla generally carries a few small teeth. The subcaudal scales are mostly in two rows. The pythons (q.v.) are restricted to the palaeotropical and Australian regions, with the sole exception of Loxocemus bicolor in southern Mexico.
Sub-family 2. Boinae. - Without supraorbital bones. The premaxilla is toothless. The subcaudal scales form mostly a single row. Widely distributed. Boa (q.v.) in tropical America and with two species in Madagascar. Eunectes murinus, the Anaconda, Charina, e.g. bottae, a small sand-snake from Oregon to California. Eryx jaculus, also a sand-snake, from North Africa to Central Asia, and extending into Greece. Enygrus, ranging from New Guinea to the Fiji Islands. Casarca dussumieri, differing from Boa chiefly by the rough and strongly-keeled scales, is confined to Round Island near Mauritius. This makes the occurrence of a species of Corallus in Madagascar less remarkable, while all the others live in Central and South America.
Family 6. Xenopeltidae. - One species, Xenopeltis unicolor, in south-eastern Asia and Malay Islands. Boulenger rightly considers this snake in various ways intermediate between the Ilysiidae, Boidae and Colubridae. The prefrontal bones are still in contact with the nasals as in the previous families, but the coronoid bones of the mandibles are absent as in the remaining families, and this loss also occurs in the Boine Charina. The most remarkable feature is the dentary bone, which is movably attached to the much-elongated articular bone (cf. Polyodontophis of Colubrinae), the movability being enhanced by the absence of the coronoid. The quadrate is short and thick, and is carried by the broad and short squamosal, which lies flat against the skull, reminding in this respect of Ilysia. The smooth, black and brown scales of the back are highly iridescent, hence the generic name of this peculiar snake, which reaches the length of one yard. Family 7. CoLuBRIDAE. - Maxillaries horizontal and forming the greater portion of the upper jaw, which is toothed like the lower jaw; coronoid of mandible absent. Pterygoids connected with the quadrates which are carried by the squamosals, and these are loosely attached to the skull. Prefrontals not in contact with the basals. Ectopterygoids present. No vestiges of limes or pelvis. This family comprises about nine-tenths of all recent species of snakes and is cosmopolitan, New Zealand being the most notable exception. The 1300 to 1400 species contain terrestrial, arboreal and aquatic forms, many of which are highly specialized.
Boulenger, adopting Dumeril's terms, has divided them into three parallel series: A. Aglypha. - All the teeth are solid, and not grooved. Harmless, non-poisonous.
The anterior maxillary teeth are grooved or "perforated." About 200 very poisonous species, e.g. cobras, coralsnakes and sea-snakes.
The second and third series containing only about 400 species, the Aglypha still present the appalling number of moo species, and even the grouping of this mass into three sub-families does not lighten the task of arranging the chaos, since one of these sub-families contains only one, and the other but a very few species. We have therefore still 1000 species, all so closely allied that they together are but of sub-family rank. They possess few reliable characters; their modifications are not weighty, and it is almost certain that some of these characters, and even combinations thereof, have been developed independently and in different countries. Many of the so-called genera, or groups of genera, are consequently not to be used either as witnesses of blood-relationship or of geographical distribution.
Some of the usual characters employed for systematic purposes, for the making of convenient keys, are the following: The number of rows of scales across the body and in a longitudinal direction; shape and structure of scales, whether smooth or with a longitudinal keel; arrangement of the shields on the head; shape of the contracted pupil. Above all, the dentition, which exhibits almost endless modifications, in most cases is difficult to ascertain and to appreciate in its subtle distinctions. Internal, skeletal characters, useless for ordinary practical purposes, are the various apophyses on the ventral side of the vertebrae and the penial armaments fancied by Cope.
It is impossible here to mention any but the more obvious genera and groups of colubrine snakes.
Series A. Aglypha. - Sub-family 1. Acrochordinae. - The few genera and species of these ugly-looking snakes are mostly aquatic, inhabiting rivers and estuaries of S.E Asia; but one, Nothopsis, lives on the Isthmus of Darien, and another, Stoliczkaia, is found in the Khasia Hills of N.E. India. Acrochordus javanicus has no enlarged ventral shields; the flat, viperish-looking head is covered with small granules, with the eyes and nostrils well on the upper surface. Chersydrus ranges from Madras to New Guinea; the body and tail are laterally compressed and form a ventral fold which is covered with tiny scales like the rest of the body. The main anatomical justification of this sub-family is given by the postfrontal bones, which, besides bordering the orbits posteriorly, are extended forwards so as to form the upper border of the orbits, separating the latter from the frontals.
Sub-family 2. Colubrinae. - The postfrontal bones are restricted to the posterior border of the orbits. The maxillary and dentary bones carry teeth on their whole length. This sub-family contains about woo species; few of them reach a length of more than two yards, some of the largest belonging to the Indian Zaocys s. Cory- phodon,which grow to 10 ft. Most of them are oviparous. Some are more or less aquatic, others are absolutely arboreal, others again prefer dry, sandy or rocky localities according to their food. The sub-family is cosmopolitan, excepting the New Zealand sub-region, and finds its natural N. limit on the permanently frozen underground, where hibernation is of course impossible. Only a few out of the more than 120 genera can be mentioned here.
Coluber in Europe, Asia and North America. C. longissimus s. flavescens s. aesculapii was probably the species held in veneration by the ancient Romans. It grows to a length of 5 ft., climbs extremely well, feeds chiefly on mice, and becomes very tame. Its coloration varies from pale golden brown to black; the scales are smooth and shiny. Its original home is Italy and S.E. Europe, whence it has spread N. into S. Germany. Its occurrence at widely distant and isolated localities was formerly supposed to be due to its introduction by the Romans. C. corals, from the S. states of N. America far into S. America, reaches 8 ft. in length. C. (Pityophis) sayi, C. catenifer and others in N. America.
Coronella, widely distributed excepting Australia and S. America. C. austriaca s. laevis, the "smooth snake" of Europe, in England, in Hampshire and Dorsetshire, eats chiefly lizards; owing to its coloration, which varies much, it is often mistaken for the viper. C. getula is one of the many N. American species. Zamenis of Europe, Asia, N. Africa, N. and Central America, with many species, e.g. Z. mucosus the Indian "rat-snake," Z. constrictor in the United States. Some species of the Central and S. American genus Urotheca bear an extraordinary resemblance in coloration to the pretty, black, red and yellow poisonous Elaps. Dendrophis of India and Australia (e.g. D. pictus of India), and Leptophis s. Ahaetulla (e.g. L. liocerus, neotropical) may be taken as examples of long and slender tree-snakes.
Tropidonotus, with near 100 species, is cosmopolitan with the exception of New Zealand. Some of the species, like the Indian T. quincunciatus and T. stolatus and the N. American T. ordinatus, are perhaps more abundant as regards the number of individuals than any other snake. T. natrix, the grass or ringed snake, is very common in Europe, including England but not Scotland or Ireland; easily recognized even at a distance by two yellow or white spots which it has behind its head. It grows rarely to a length of 4 ft.; it never bites, and feeds chiefly on frogs, toads and fishes, but mice are never taken. Its eggs, which are of the size and shape of a dove's egg, are from fifteen to thirty in number, are deposited in mould or under damp leaves, and are glued together into one mass.
Polyodontophis of Madagascar, S.E. Asia and Central America is remarkable for having the dentary bones loosely attached to the apex of the elongated articular bone. Calamaria of Indo-China is an example of burrowing snakes, with a short tail and small eyes; in Typhlopophis of the Philippines the eyes are concealed.
Sub-family 3. Rhachiodontidae, represented by Dasypeltis scabra of tropical and S. Africa. Characterized by possessing only a few teeth, on the posterior part of the maxillaries, on the palatines and Coronelline Nymphophidium, the same effect is reached by two prominences at the base of the skull.
Series B. Opisthoglypha. - One, or a few, of the posterior maxillary teeth have a groove or furrow in front, which conducts the secretion of the enlarged upper labial glands. They are all more or less poisonous, paralysing their prey before, or during the act of swallowing; the poison-fangs standing so far back in the mouth, these snakes cannot easily inflict wounds with them on man; moreover, the poison is not very strong and not available in large quantities. It may well be doubted whether Opisthoglypha form one genuine group instead of a heterogeneous assembly. They comprise about 300 species of terrestrial, arboreal and aquatic forms, and as a group they are almost cosmopolitan, including Madagascar, but excepting new Zealand.
Sub-family t. Dipsadomorphinae. - Nostrils lateral; dentition well developed. Long-tailed, terrestrial and arboreal forms. The tree-snakes are mostly green above with the under parts white or yellow.
Coelopeltis, with concave, or grooved scales; C. lacertina s. monspessulanus, one of the largest European snakes in Mediterranean countries and south-western Asia.
Dipsadomorphus, Dipsas, Leptognathus, Dryophis, Dendrophis and other closely allied genera are typical, very long-bodied and longtailed tree-snakes, chiefly tropical. The graceful form of their body, the elegance and rapidity of their movements, and the exquisite beauty of their colours have been the admiration of all who have had the good fortune to watch them in their native haunts. The majority lead an exclusively arboreal life; only a few descend to the ground in search of their food. They prey upon every kind of arboreal animal - birds, tree-frogs, tree-lizards, &c. All seem to be diurnal, and the larger kinds attain to a length of about 4 ft. The most beautiful of all snakes are perhaps certain varieties of Chrysopelea ornata, a species extremely common in the Indian Archipelago and many parts of the continent of tropical Asia. One of these varieties is black, with a yellow spot in the centre of each scale; these spots are larger on the back, forming a series of tetrapetalous flowers; the head is similarly ornamented. Another variety has a red back, with pairs of black crossbars, the bands of each pair being separated by a narrow yellow space; sides brown, dotted with black; belly dark green, the outer portion of each ventral shield being yellow,. with a blackish spot.
The features by which the treesnakes are distinguished are still more developed in the whip-snakes (Dryophis), whose excessively slender body has been compared to the cord of a whip. Although arboreal, like the former, they are nocturnal in their habits, having a horizontal instead of a round pupil of the eye. They are said to be of a fierce disposition, feeding chiefly on birds. In some of the species the elongate form of the head is still more exaggerated by a pointed flexible appendage of the snout (Passerita), which may be nearly half an inch in length, or leaf-like, as in the Madagascar Langaha. The Mexican Trimorphodon much resemble viperine snakes with the flat, triangular head, narrow neck, slit-like pupil and pugnacious disposition. A still more remarkable resemblance exists in the shape and striking, red, black and yellow coloration between Scolecophis aemulus of Chihuahua and the poisonous Elaps fulvius, the American coral-snake, but Cope has been careful to point out that these two creatures are not known to inhabit the same district.
Sub-family 2. Elachistodonidae.- Represented by Elachistodon westermanni of Bengal, with the same peculiar dentition and with sharp hypapophyses on the vertebrae of the lower neck, as described of Dasypeltis (see above).
Sub-family 3. Homalopsinae. - The nostrils of these absolutely aquatic, viviparous snakes are valvular and placed on the upper surface of the snout. The eyes are small, with vertical pupils. About two dozen ugly-looking species inhabit rivers and estuaries from Bengal to Australia. Cerberus rhynchops; Hypsirhina plumbea, Homalopsis; Hipistes hydrinus of Siam has a compressed body, and much resembles the Hydrophinae in general appearance and its partly marine life. Herpeton of Cambodia has a pair of long tentacles on the snout and is said to have a partly vegetable diet!
Series C. Proteroglypha. - The anterior maxillary teeth are deeply grooved, or so folded as to appear hollow or perforated. Behind these enlarged poison-fangs follows a series of smaller, solid FIG. 7. - Dasypeltis unicolor, in the act of swallowing an egg. Nat. size.
dentaries; some of the vertebrae in the lower region of the neck have strongly developed hypapophyses (not provided with a cap of enamel, as has often been asserted), which are directed forwards and pierce the oesophagus. The principal diet of these peculiar snakes seems to consist of eggs. In Cape Colony they are known as "eyervreter," i.e. egg-eater. A snake, scarcely 20 in. in length, and with a body not thicker than a man's little finger, is able to swallow a hen's egg, a feat which seems quite impossible. As the egg passes at last through the alarmingly distended neck, the snake makes some slight contortions and the swelling collapses, the shell having been filed through by the saw-like apparatus. Whilst the contents are thus retained without loss, the crumpled shell is then vomited out. This peculiar arrangement occurs also in an Indian snake, Elachiston, which represents, however, a sub-family of the Opisthoglypha. In another, probably also egg-eating snake, the Indian teeth, hence the term "proteroglypha," which is intended to mean that the anterior teeth are grooved. These snakes are all very poisonous, mostly viviparous and found in all tropical and subtropical countries, with the exception of Madagascar and New Zealand.
Sub-family I. Elapinae. - Terrestrial, with a cylindrical tail, comprising about 150 species which have been grouped into numerous genera, mostly upon very slight differences. The most remarkable are the following. Naha tripudians and N. haje, the cobra (q.v.). The largest species is the N. bungarus s. elaps, the "hamadryad," "snake-eating cobra," or king-cobra of Indian countries, reaching more than 12 ft. in length, and living mainly upon other snakes. Sepedon haemachates, of S. Africa, is named by the Boers "roode FIG. 8. - Indian Whip-Snake. Passerita mycterizans. koper kapel" or "ring-hals," i.e. banded neck, the latter name. being, however, often applied also to the cobra. It resembles in colour some varieties of the latter snake, and, like this, it has the power, though in a less degree, of expanding its hood. But its scales are keeled and its form is more robust. It is equally active and courageous, not rarely attacking persons who approach too near to its resting-place. In confinement it evinces great ferocity, opening its mouth and erecting its fangs, from which the poison is seen to flow in drops. During such periods of excitement it is even able, by the pressure of the muscles on the poison-duct, to eject the fluid to some distance; hence it shares with the cobra a third Dutch name, that of "spuw slang" (spitting snake). It grows to a length of 2 or 3 ft. Another kind is the "schapsticker" (sheep stinger), S. rhombeatus. It is extremely common in S. Africa, and extends far N. along the E. as well as W. coast. It is of smaller size than the preceding, and causes more injury to animals, such as sheep, dogs, &c. than to man. It varies in colour, but a black mark on the head like an inverted V remains nearly always visible.
The species of Bungarus, four in number, are extremely common in India, Burma, and Ceylon, and are distinguished by having only one row of undivided sub-caudal shields. Three of the species have the body ornamented with black rings, but the fourth and most common (B. coeruleus), the "krait" of Bengal, possesses a dull and more uniform coloration. The fangs of the bungarums are shorter than those of the cobras, and cannot penetrate so deeply into the wound. Their bite is therefore less dangerous and the effect on the general system slower, so that there is more prospect of recovery by treatment. Nevertheless, the krait is probably the most destructive snake to human life in India, since it is very common and often creeps into the houses. Doliophis intestinalis of Indo-China has enormously developed poison glands, which extend down the whole anterior third of the body, in front of the heart.
No part of the world possesses so many snakes of this sub-family as Australia, where, in fact, they replace the non-venomous colubrine snakes; many of them are extremely common and spread over a considerable area. Fortunately the majority are of small size, and their bites are not followed by more severe effects than those from the sting of a hornet. Only the following are dangerous to man and larger animals: the "death-adder," Acanthopis antarcticus, easily recognized by the peculiar end of the tail which is compressed and terminates in a thin horny spine; common throughout Australia to the Moluccas, scarcely one yard in length; the "black snake" (Pseudechis porphyriacus),likewise common throughout the Australian continent, especially in low marshy places, and upwards of 6 ft. in length; it is black, with each scale of the outer series red at the base; when irritated it raises the fore part of its body and flattens out its neck like a cobra, the females are sometimes known as "brown adders"; the "tiger-snake," Notechis scutatus (s. Hoplocephalus curtus), with a similar distribution, and also common in Tasmania, from 5 to 6 ft. long, and considered the most dangerous of the tribe. Good descriptions and figures of all these snakes are given in Krefft's Snakes of Australia (Sydney, 1869, t 40 Several genera of the Elapinae lead a more or less burrowing life; their body is of a uniform cylindrical shape, terminating in a short tail, and covered with short polished scales; their head is short, the mouth rather narrow, and the eye small. They are the tropical American Elaps, the Indian Callophis, the African Poecilophis and the Australian Vermicella. The majority are distinguished by the beautiful arrangement of their bright and highly ornamental colours; many species of Elaps have the pattern of the so-called coral-snakes, their body being encircled by black, red and yellow rings - a pattern FIG. to. - A Poisonous Snake (Elaps fulvius) swallowing a similarly coloured Opisthoglyphous Snake (Homalocranium semicinctum). which is peculiar to snakes, venomous as well as non-venomous, of the fauna of tropical America. Although the poison of these narrowmouthed snakes is probably as virulent as that of the preceding, man has much less to fear from them, as they bite only under great provocation. Moreover, their bite must be frequently without serious effect, owing to their narrow mouth and the small size of their poisonfangs. They are also comparatively of small size, only a few species rarely exceeding a length of 3 ft., for instance Elaps fulvius, which extends into the S. states of N. America.
FIG. 9. - Head of Herpcton tentaculatum. Sub-family 2. Hydrophinae. - Tail laterally compressed; marine. Of sea-snakes some fifty species are known. All are inhaoitants of the tropical Indo-Pacific ocean, and most numerous in and about the Persian Gulf, in the East Indian Archipelago, and in the seas between S. Japan and N. Australia. One species which is extremely common (Pelamis bicolor), and which is easily recognized by the black colour of its upper and the yellowish tints of its lower parts (both colours being sharply defined), has extended its range W. to the sea round Madagascar, and E. to the Gulf of Panama. One species, however, Distira semperi, is confined to the landlocked freshwater Lake Taal at Luzon in the Philippines. Sea-snakes are viviparous and pass their whole life in the water; they soon die when brought on shore. The scales are very small, often very much reduced, and there are frequently no enlarged ventrals on the compressed belly, but Platurus has broad ventrals. Their motions in the water are almost as rapid as they are uncertain and awkward when the animals are removed out of their proper element. Their nostrils are placed quite at the top of the snout. These openings are small and provided with a valve interiorly, which is opened during respiration, and closed when the animal dives. They have very capacious lungs, extending backwards to the anus; by retaining air in these extensive lungs they are able to float on the surface of the water and to remain under water for a consider able length of time. Sea-snakes shed their skin frequently; but it peels off in pieces as in lizards, and not as in the freshwater snakes, in which the integuments come off entire. Several species are remarkable for the extremely slender and prolonged anterior part of the body, and very small head. The eye is small, with round pupil, which is so much contracted by the light when the snake is taken out of the water that the animal becomes blinded and is unable to hit any object it attempts to strike. The tongue is short, and the sheath in which it lies concealed opens near to the front margin of the lower jaw; scarcely more than the two terminating points are exserted from the mouth when the animal is in the water. The mouth shuts in a somewhat different way from that of other snakes: the middle of the rostra' shield is produced downwards into a small lobule, which prevents the water from entering the mouth; there is generally a small notch on each side of the lobule for the passage of the two points of the tongue. The food of sea-snakes consists entirely of small fish; among them species with very strong spines. As all these animals are killed by the poison of the snake before they are swallowed, and as their muscles are perfectly relaxed, their armature is harmless to the snake, which begins to swallow its prey from the head, and depresses the spines as deglutition proceeds. Sea-snakes belong to the most poisonous species of the whole order. Accidents are rarely caused by them, because they are extremely shy and swim away on the least alarm; but, when surprised in the submarine cavities forming their natural retreats, they will, like any other poisonous terrestrial snake, dart at the disturbing object; and, when out of the water, they attempt to bite every object near them, even turning round to wound their own bodies. They cannot endure captivity, dying in the course of two or three days, even when kept in capacious tanks. The greatest size to which some species attain, according to positive observation, is about 12 ft., and therefore far short of the statements as to the length of the so-called sea-serpents (q.v.). Boulenger has written an interesting account of sea-snakes in Natural Science, i. (1892), p. 44 seq.
Family 8. Amblycephalidae. - The pterygoids are widely separated from the quadrates, not reaching beyond the level of the occipital condyle. This condition can be ascertained without dissection, when the mouth is opened widely. The squamosals are reduced to pad-like vestiges. Otherwise these snakes agree with the aglyphous Colubridae. Externally they are easily distinguished by the absence of a longitudinal groove on the skin. The head is thick, very distinct from the neck and the pupil is vertical, so that these harmless snakes look rather viperish. About 30 species, with several genera, are known from the oriental and neotropical regions. Amblycephalus, e.g. monticola, with compound body, in S.E. Asia.
Family 9. Viperidae.-The maxillaries are very short, movably pivoting upon the prefrontals and also attached to the ectopterygoids, so that they can be erected together with thelarge poison fangs, which, besides reserve teeth, are the only maxillary teeth. There are also teeth on the palatines, anterior portion of the pterygoids, and on the short dentaries. The short squamosals are very loosely attached to the skull. The prefrontals are not in contact with the nasals. The poison-fangs are "solenoglyphous," perforated, having a wide hole on the anterior side at the base, in connexion with the duct of the large, paired, poison-glands, the presence of which adds considerably to the characteristic broadness of the head. The hole leads into a canal, which opens as a semi-canal towards the end of the tooth. The supply of reserve teeth is indefinite; frequently one or two are lying ready and of equal size to the functional fangs.
All the Viperidae are very poisonous and all, except the African Atractaspis, are viviparous. They include terrestrial, semi-aquatic and burrowing types; none of them with any signs of degradation; on the contrary they belong to the most highly organized of snakes. The family is cosmopolitan, excepting Madagascar and the whole of the Australian region.
Sub-family t. Viperinae, vipers (q.v.) or adders. - Without an external pit between eye and nose, and the maxillary bone is not hollowed out above. Absolutely restricted to the Old VL orld, with 9 genera comprising about 40 species.
Sub-family 2. Crotalinae. - With a deep cavity or pit on either side between the eye and the nose, lodged in the hollowed-out rr.axillary bone. The lining of these pits is amply supplied with branches from the trigeminal nerves, but the f unction is still quite unknown. About 60 species of pit-vipers are recognizable. They can easily be divided into 4 genera: Crotalus and Sistrurus with a rattle at the end of the tail and restricted to America (see Rattlesnake); secondly, pit-vipers without a rattle: Ancistrodon, with large shields covering the upper surface of the head; with about to species, e.g. A. halys in the Caspian district, others in the Himalayas, Ceylon and Sunda islands. Notable American species are the following: A. piscivorus, the "water-viper" front Carolina and Indiana to Florida and Texas. This creature is semi-aquatic and lives chiefly on fishes; it grows to a length of about 5 ft.; the general colour is reddish to dark brown, FIG. 12. - Lachesis viridis of India.
even blackish, with darker cross-bands or C-shaped markings; a dark, light-edged band extends from the eye to the angle of the mouth. The under parts are yellowish, more or less spotted or quite black. A. contortrix the "moccasin-snake" or "copper-head," so called because of its yellow to pink or pale-brown ground colour, with dark crossbars or triangular marks. The under surface is yellow to reddish, with dark specks. Full-grown specimens are about t yd. in length. The moccasin-snake ranges fromMassachusetts and Kansas to Florida and Texas and into Mexico, preferring swampy localities or meadows with high grass, where it hunts for small mammals and birds. It is easily distinguished from other North FIG. t I. - Sea-Snake, Pelamis bicolor. American pit-vipers by the possession of a loreal shield, i.e. a shield intercalated between the two preoculars and the posterior nasal; below the loreal lies the pit.
The moccasin and the water-viper have occasionally been mentioned under the name of Trigonocephalus cenchris, one of the many synonyms.
Lachesis has the upper surface of the head covered with very small shields, or with scales, and contains about 40 species, in S. and Central America, the Antilles and also in S.E. Asia. The most ill-famed is L. s. Bothrops s. Craspedocephalus lanceolatus, which inhabits the greater part of S. America, extending into Mexico and the Lower Antilles. notably Martinique, Guadaloupe and Santa Lucia, where it is known as the "Fer de Lance"; Mexicans call it "rabo de hueso" or bone-tail, on account of the curiously coloured and spike-like tip of the tail. It is a very quick and highly irascible beast and even known to turn on its pursuer. It grows to a length of 6 ft., lives in swamps, plantations, forests, on the plains and on the hills, and is very prolific, producing dozens of young, which at birth are 10 in. long and as vicious as their parents.
L. s. Trimeresurus gramineus s. viridis s. erythurus is one of the Asiatic species, ranging over the whole of India to Hong-kong, Timor and even to the Andaman and Nicobar Islands. It is arboreal, bright green above; the end of the prehensile tail is usually bright red. (H. F. G.)
From Britannica 11th Edition (1911) 
ZWI signed:
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