Page:EB1911 - Volume 25.djvu/306

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290
SNAKES


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. corais, from the S. states of N. America far into S. America, reaches 8 ft. in length. C. (Pity- ophis) 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. iiocerus, 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 oi the elongated articular bone. Calamaria of Indo-China is in 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

Fig. 7. — Dasypeltis unicolor, in the act of swallowing an egg

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 snate 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, Eiachiston, which represents, however, a sub-family of the Opistho- glypha. In another, probably also egg-eating snake, the Indian Coronelline Nymphophidiutn, 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; more- over, the poison is not very strong and not available in large quan- tities. 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 1. 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 long- tailed tree-snakes, chiefly tropical. The graceful form of their body, the elegance and rapidity of their movements, and the ex- quisite 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 Chry- sopelea ornata, a species extremely common in the Indian Archi- pelago 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 tree- snakes 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 dis- position, feeding chiefly on birds. In some of the species the elongate form of the head is still more ex- aggerated 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, tri- angular 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 plum-bea, Homalopsis; Hipistes hydriniis 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