242 THE ANATOMY OF VEETEBEATED ANIMALS. 



nidiments of a pelvis, and tlie latter Snakes even possess 

 very short representatives of hind limbs terminated by 

 claws. 



The teeth of the Ophidia are short and conical, and 

 become ankylosed to the bones by which they are sup- 

 ported. They may be developed in the premaxillaiies, max- 

 illaries, palatines, pterygoids, and the dentary piece of the 

 mandible, but their presence in the premaxillaries is excep- 

 tional. In JJropeltis and some other genera, there are no 

 palatine teeth ; and in the egg-eating African snake, Bachio- 

 don, the teeth are small and iTidimentary upon all the bones 

 which usually bear them. But the inferior spines of eight 

 or nine of the anterior vertebrae are long, and tipped, at 

 their apices, with a dense enamel-like substance. These 

 project through the dorsal wall of the oesophagus into its 

 cavity, and the eggs, which are swallowed whole, are thus 

 broken in a position in which all their contents must neces- 

 sarily be saved. 



In the majority of the non- venomous Snakes the teeth are 

 simply conical, but in the others, and in all the poisonous 

 Snakes, some of the maxillary teeth (which are usually 

 longer than the rest) become grooved in front. In the 

 Solenoglyphia, or Vipers and Rattlesnakes, the maxillary 

 teeth are reduced to two or three long fangs, the groove in 

 the front of which is converted into a canal open at each 

 end, by the meeting of its edges. The teeth of the Snakes 

 are replaced by others which are developed close to the 

 bases of the old ones. 



Opliidia are not known in the fossil state before the 

 older tertiaries. 



Y. The IcHTHTOSAURiA. — In its general form Ichthyo- 

 saurus presents a good deal of resemblance to a Cetacean. 

 The head is enormous, and passes at once into the trank, 

 so that there is no more appearance of a neck than in a 

 Porpoise, and the body tapers off behind, much as would 

 happen in the latter animal were it devoid of a caudal fin. 

 Indeed, there is some reason to suspect that the tail of 



