EXTINCT GROUPS OF SCALED REPTILES 2613 



expanded bases. The bones of the shoulder girdle and pelvis were more or less 

 imperfectly developed, and the limbs were modified into paddles or flippers, with 

 the toes inclosed in a common skin, and devoid of claws. There were either nine 

 or ten vertebrae in the neck; and whereas, in some cases, the vertebrae resembled 

 those of snakes, in other instances they lacked the additional articulations dis- 

 tinguishing the latter. It will be unnecessary to particularize the various genera 

 of these reptiles, but it may be mentioned that while some of the better-known 

 forms have been described as Mosasaurus, others have received the names of 

 Liodon and Clidastes. They appear to have inhabited the Cretaceous seas of all 

 parts of the world, having been obtained from regions as far apart as England, 

 New Zealand, and Argentina; and while some attained a length of between twenty- 

 five and thirty feet, others were not more than eight or ten. Then, again, while in 

 some cases the jaws were armed with powerful teeth to their extremities, other 

 forms had a long, toothless beak. 



