THE VI PER IN E SNAKES. 73 



species of this genus inhabit India, and the rest are found in the 

 Indo-Chinese and Malayan countries, one of the most common of 

 them (C. iiitestinalis) having likewise been received from the 

 Philippines. The C. nigrescens of the mountains of southern India 

 attain to four feet in length, but they are mostly about half that size, 

 or even smaller. 



Lastly, we arrive at 



The Viperine Snakes, 



which have a long, perforated, erectile fang on the maxillary bone, 

 which is extremely short and bears no other teeth. This is described 

 in greater detail subsequently (pp. 87 and 88). They are arranged 

 under the two families, Crotalidce and Viperidce. 



The Crotalidce, or Pit Vipers, have the body robust, the tail of 

 moderate length, or rather short, sometimes prehensile ; head broad, 

 sub-triangular, frequently scaly above or imperfectly shielded ; a deep 

 pit on the side of the snout, between the eye and nostril ; the eye of 

 moderate size, with vertical pupil. They are viviparous. The Pit 

 Vipers are found only in Asia and America ; those of the New 

 World surpassing the Asiatic species in size, and therefore they are 

 much more dangerous. Some live in bushes, others on the ground. 

 A rudiment of the curious caudal appendage of the American Rattle- 

 snake is found as a simple spine-like scale in the Asiatic species, 

 constituting the genus Halys. 



Some have the head covered with scales, having small shields on 

 the edge of the forehead and brows ; the cheeks are scaly, and the 

 tail ends in a spine. Of these the American genus Craspedocephalus 

 and the Asiatic genus Trimeresurus have the sub-caudal plates two- 

 rowed to the tip. 



The genus Craspedocephalus comprises the terrible Fer-de-Lance of 

 certain islands in the West Indies and of the mainland of South 

 America, where four other species are recognised — one of them being 

 found as far north as Mexico.] 



The Fer-de-Lance (C. lanceolatus, Fig. 18) attains to a length of 

 nearly six feet ; its colour generally yellow, sometimes greyish, or 

 even marbled with brown ; the head, which is large, is remarkable 

 for a triangular space, the three angles of which are occupied by the 

 muzzle and the two eyes. 



This space, raised at its front edge, represents the head of a 

 lance, large at its base and slightly rounded at the summit. On 

 each side of the upper jaw, one, sometimes two, and even three, 

 fangs are visible ; all of which the animal makes use of for the pur- 



