14 GUIDE TO REPTILES AND AMPHIBIANS. 



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

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

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

 Case 20. 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. 



Shown in IV. DoLiCHOSAURiA. Includes several snake-like forms typified 



Geological 1^^. fjQiicJiosaurus of the English Chalk, which was over a 



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



by a bony suture, two sacral vertebra3, a long neck, and the 



limbs partially modified into paddles. 



V. Pythonomorpha. Typified by the gigantic Moscmmrus 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 SQUAMATA.* 



a. Sub-order Ophidia. 

 Family Bo idee. 

 „ TyphlopidcB. 

 „ GlauconiidcB. 

 „ IlysiidcB. 

 ,, Uropeliidce. 

 „ Xenopeltidce. 

 „ Coluiridce. 

 „ AmhlycephalidcB. 

 „ Viper idee. 



b. Sub-order Lacertilia. 

 Family GerJcouidce. 

 „ EublepharidcR. 

 „ UroplatidcB. 

 „ Pygopodidm. 

 „ Agamidce. 

 „ Iguanidm. 

 „ JCenosauridce. 

 „ Zonuridce. 

 „ Anguidce. 



* 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. 



