CHAPTER XIII 



SAURIA, continued OPHIDIA SNAKES 

 Order II. OPHIDIA SNAKES. 



Saurians which have the right and left halves of the lower jaw 

 connected ty an elastic band. 



THE Snakes are the most highly specialised branch of the Sauria, 

 from which they do not differ in any fundamental characters. 

 The chief modifications consist in the absence of the limbs and 

 limb -girdles (a feature intimately correlated with the much- 

 elongated body), and in the swallowing apparatus. The reduc- 

 tion of the limbs and the elongation of the body also occurs in 

 many Lacertilia ; in several of the older families of Snakes (e.g. 

 Typhlopidae and Boidae) vestiges of the hind -limbs and even 

 of the pelvis are still in existence. Even the peculiar suspensorial 

 apparatus of the lower jaw approaches that of the Lacertilia 

 in the burrowing Ilysiidae and in Xenopeltis. 



In the majority of the Snakes the quadrate is very loosely 

 suspended from the squamosal (by some authorities homologised 

 with the supratemporal bone of other reptiles), and this again 

 is loosely attached to the lateral parietal region of the skull, 

 placed horizontally, and elongated so far backwards that the 

 vertically placed quadrate lies in a plane behind the skull. In 

 most Snakes the elongated pterygoids are loosely attached to the 

 inner side of the distal end of the quadrates, and they also often 

 touch the mandibles. The whole palatal apparatus is movably 

 attached to the skull, except in some burrowing families. The 

 right and left pterygoids and palatines are widely separated from 

 each other. The pterygoids and maxillaries, connected by the 

 ectopterygoids, are absent, owing to reduction, in the Typhlo- 



