14 



GUIDE TO KEPTILES AND AMPHIBIANS. 



Case 20. 



Shown in 

 Geological 

 Depart- 

 ment. 



are transparent and fixed as in Snakes, while the scales may 

 be rudimentary or wanting. In some of the limbless burrow- 

 ing forms the quadrate-bone has become more or less fixed. 

 III. Rhiptoglossa, or Chameleons. These differ from Lizards 

 in several particulars ; notably the separation of the toes 

 into two groups of three and two respectively, so that the 

 feet form most efficient grasping organs, and the long 

 extensile, club-shaped tongue. The skeleton lacks clavicles 

 and interclavicle ; and there are several osteological peculi- 

 arities in the skull, which is casque-shaped and often studded 

 with tubercles. 



In addition to the above, there are the two following extinct 

 sub-orders, the members of which were marine. 



IV. Dolichosaubja. Includes several snake-like forms typified 

 by Dolichosaurus of the English Chalk, which was over a 

 yard in length, with the two halves of the lower jaw united 

 by a bony suture, two sacral vertebrae, a long neck, and the 

 limbs partially modified into paddles. 



V. Pythonomorpha. Typified by the gigantic Mosasaurus of 

 the Upper Cretaceous, and characterised by the ligamentous 

 union of the right and left halves of the lower jaw, the 

 presence of only one sacral vertebra (with which the pelvis 

 has no connection), and the completely paddle-like form of 

 the limbs. 



The following are the sub-divisions of the 



Order 



a. Sub-order Ophidia. 

 Family Boidce,. 



„ Typhlopidw. 

 „ Glauconiidw. 

 „ Itysiidm. 

 ,, Uropeltid(B. 

 „ Xenopeltidw. 

 „ Colubridce,. 

 „ Amity ceplialidce. 

 „ ViperidcR. 



SQUAMATA.* 



1). Sub-order Lacertilia. 

 Family Geckonidm. 



Eublepharidce. 



Uroplatidw. 



PygopodidcB. 



Agamidm. 



Iguanidm. 



Xenosaaridm. 



Zonuridm. 



Anguidas. 



* In consequence of the Cases not being all of a uniform depth, it has been 

 found impossible to adhere strictly to this arrangement of the families. 



