Class 4. Reptilia. Order 2. Ophidia. 



425 



species in the Indian and Pacific Oceans ; iisually Small (rarely longer tlian the 

 Ringed Snake, often smaller) ; their bite is dangerous. 



5. The Solenoglypha or Vipers. The large poison fang is the only tooth in 

 the maxilla, it has no groove anteriorly ; the head is usually broad behind, and 

 sharply marked off from the body. 



a. Common Yiper or Adder {Vipera herus), with a zig-zag line 

 down the back ; viviparous ; 

 abvindant in England, es- 

 pecially upon sandy heaths. 

 The somewhat larger Sand- 

 viper {Vipera ammodytes), 

 with upwardly directed pro- 

 cess on the snout, lives on 

 the Mediterranean coasts, in 

 Austria, and in South Bavaria, 



h. The Pit Vipers 

 {Crotalidx) are characterised 

 by the possession of a deep 

 pit on either side between the 

 eye and the nans. To this 

 gi'oup belong most of the 

 dangerous snakes occurring in 

 warm countries. The Rattle- 

 snake (Crotaliis) differs from 

 the rest, in possessing at the 

 tail end, several loose rattling, 

 horny caps, fitting into one 



another, the remains of cast skins (see Fig. 350). Several species (to over 2 m.) 

 in North and South America. Species of Trigonocephalus, usually smaller, but 

 very dangerous, live in India and America. 



Fig. 350. Tail end of a Crotalus with eleven 

 caps (1 the oldest, 11 the youngest). B the same 

 cut through longitudinally, v vertebral column, 

 v' several fused vertebrae, forming the last joint of the 

 vertebral column (the surrounding soft parts dotted) ; 

 the caps in se'-tion indicated by a thick Une. As a 

 comparison of the two figures shows, only the anterior 

 portion of each cap, with the exception of the oldest, 

 projects as an arched ring, the re*t being covered by 

 the next older cap. — After Garman. 



Order 3. Chelouia {Testudinata). 



The edentulous jaws are covered by a borny sheatb witb a sharp 

 edge. Large dermal plates are present, which usually fit into 

 one another at the edges, so as to form a continuous bony shell 

 round that part of the body. There is a large opening in front for 

 the head and fore limbs, and behind for the tail and hind limbs. 

 Dorsally, there are three longitudinal rows of bony plates, of which 

 the middle row is connected with the vertebrse (vertebral plates), 

 whilst the two others are fused with the ribs of each side, one for 

 •each rib. Besides these three rows there is, externally, a series of 

 small marginal plates. Ventrally, there are two rows ; there is 

 an anterior' unpaired piece, probably corresponding to the epi- 

 sternum of other Reptiles, and in front of this a pair, which may 

 represent the clavicles. These bony plates do not form so complete 

 a shell in all Chelonians ; in the Turtles, for instance, the plates do 

 not fit close together, but large portions of unossified leathery skin 

 are left between their edges. The regions in which the dermal 

 armour lies are usually covered, externally, by large horny shields 



