xill ELACHISTODONTINAE HOMALOPSINAE 625 



fourth and fifth maxillary teeth are enlarged, followed by an 

 interspace, then follow several small teeth, and lastly the two 

 enlarged, grooved teeth. The sixth mandibular tooth is very 

 long, separated by a space from the much smaller posterior teeth. 

 The general colour of this sand-loving snake is pale brown or 

 grey above with small spots or streaks on the trunk, and with a 

 large black patch behind the head extending over the sides of the 

 neck, hence the specific name. The under parts are bright red or 

 yellowish, sometimes spotted with black. Total length under 2 feet. 



Sub-Fam. 2. Elachistodontinae. — With only a few teeth on 

 the posterior part of the maxillary and dentary bones, and on 

 the palatines and pterygoids. Some of the vertebrae in the 

 thoracic region have much - developed unpaired hypapophyses, 

 which are directed forwards and pierce the dorsal wall of the 

 gullet. In this respect Machistodon westermanni, of Bengal, the 

 only species, bears a striking resemblance to the South African 

 Xglj'p'hodonX, Dasz/peltis (see p. 622), and it is probable that this 

 apparently very rare Indian snake also swallows eggs. It is 

 brown above, with a yellowish vertebral stripe ; yellowish below. 



Sub-Fam. 3. Homalopsinae. — The nostrils of these absolutely 

 aquatic and viviparous snakes are valvular, and are situated on the 

 upper surface of the snout. The eyes are small with vertical 

 pupils. The two dozen species, mostly very ugly, inhabit the 

 rivers and estuaries of the East Indies from Bengal to North 

 Australia. Some species have very small and narrow ventral 

 scales, recalling the Hydrophinae, or the burrowing snakes, none 

 of which use their ventral scales for locomotory purposes. 



Eomalopsis luccata, Cerlerus rhymhops and Hypsirliina, e.g. 

 H. plumbea, have well-developed ventral scales ; the other scales 

 of the first two genera are keeled, those of the third are smooth. 

 In Hipistes the whole head is covered with very small scales ; all 

 the scales of the body are smooth except the very narrow 

 ventrals, which have double keels. H. hijdrinus, of Siam and the 

 Malay Peninsula, has a compressed body, and in its general 

 appearance much resembles the Hydrophinae. It lives, like its 

 allies, upon fishes, and it swims far out into the sea. 



Series 0. PROTEROGLYPHA. 



The anterior maxillary teeth are deeply grooved, or so folded 



9 q 

 VOL. VIII 



