HOMALOPSID.^. 275 



without tail, and said to be from Siam. Cope says that it is similar in appearance to a 

 Tropidonotus, and describes it as follows : — 



" Muzzle rather narrow ; rostral i^late nearly as high as broad. Vertical rather large, its lateral borders 

 converging, presenting a right angle posteriorly. Nasals equal in size. Loreal trapezoid, posterior 

 inferior angle acute. Preocular not reaching vertical. Three postoculars. Eight superior labials, eye 

 resting on fourth and fifth. Nine or ten inferior labials ; postgeneials sepai-ated, longer tlian the anterior. 

 Scales in nineteen longitudinal rows, elongate, emarginate at the tip, those of the external row not larger 

 than the others, keeled. Gastrosteges 152. 



" Olivaceous above, shading into leek-green upon the flanks, and greenish white upon the belly. A 

 vertebral band of light green bordered with black extends from the occipital plates to the origin of the 

 tail, involving one row and two half rows of scales. Another, narrower and paler band extends upon tlie 

 third and fourth rows of scales upon each side from the neck to origin of the tail ; this band is bounded 

 above by an interrupted narrow black border. Temporal region lively green, plates of liead and muzzle 

 tinged with fulvous. Upper labials and preocular white : a narrow black postocular vitta." 



FAMILY OF FRESHWATER SNAKED— HOilLJLOPSW^. 



Body of moderate length, cylindrical or slightly compressed ; head rather 

 thick, hroad, not very distinct from neck ; tail strong', of moderate length, 

 tapering, more or less prehensile and compressed at its root, especially in 

 the males. Scales subequal in size, not much imbricate ; ventrals rather 

 narrow, sometimes hicarinate ; anal bifid; subcaiidals two-rowed. Eve 

 small. The nostrils are situated anteriorly on the upper surface of the 

 head, small, provided with a valvule; the nasals are much developed, so as 

 considerably to reduce the anterior frontals in size, which, frequently, are 

 confluent into a small single shield, or, if double, are very small, triangular. 

 The other shields of the head also frequently deviate from the arrangement 

 typical in the Colubrine Snakes. Cleft of the mouth of moderate width. 

 All the Indian freshwater snakes of this fiimily have a grooved fang- at the 

 hinder extremity of the maxillary bone. 



The snakes of this family are thoroughly aquatic, and are only occasionally found on 

 the beach ; several of them even enter the sea, and in several points of their organization 

 approach the truly marine snakes, with which they have been associated in Gray's system. 

 They may easily be recognized by the position of the nostrils on the top of the snout, 

 which enables them to breathe by raising but a very small part of their head out of the 

 water; it is the same arrangement as that in the Crocodiles, Sea-snakes, and other aquatic 



2 n2 



