Page:EB1911 - Volume 25.djvu/305

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SNAKES


of which, for instance, 7". braminus ranges from southern Asia, the islands of the Indian Ocean and the Malay Islands to southern Africa.

Family 2. Gl auconiidae. — 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 dis- tensible. The pelvic girdle and the hind-limbs show the least reduction found in any recent snakes, ilia, pubes and ischia being still distin- guishable, the last even retaining their sym- physis, and there are small vestiges of the femurs. About 30 species, mostly of the genus Glaucoma, in south-western Asia, Africa, Madagascar, the Antilles and both Americas, G. dulcis ranging northwards into Texas, G. humilis 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

p IG (, Three between the scales on either side of the vent,

Views of Head of as ' n tne Boidae. The small eyes are some- Typhlops bra- times covered by transparent shields. About minus ( I n d i a ) " half-a-dozen species only are known in South magnified. ' America, Ceylon, the Malay Islands and Indo-

China. They are viviparous like the Typhlo- pidae, 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 mountain- forests. 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 squa- mosal, 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 Python- inae 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 pre- maxilla generally carries a few small teeth. The subcaudal scales are mostly in two rows. The pythons (q.v.) are restricted to the palaeo- tropical and Australian regions, with the sole exception of Loxocemus bicolor in southern Mexico.

Sub-family 2. Boinae. — Without supraorbital bones. The pre- maxilla 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 (q.v.), 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. Xenopei.tidae. — 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 limbs 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.

B. Opislhoglypha. — One or more of the posterior maxillary teeth are grooved. Most of these snakes, which number about 300 species, are moderately poisonous.

C. Proteroglypha. — -The anterior maxillary teeth are grooved or " perforated." About 200 very poisonous species, e.g. cobras, coral- snakes and sea-snakes.

The second and third series containing only about 400 species, the Aglypha still present the appalling number of 1000 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 t he con- tracted 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 en- larged 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 1000 species; few of them reach a length of more than two yards, some of the largest belonging to the Indian Zaocys s. Coryphodon, 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-familv 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. longissimuss. 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