SQUAMATA 



!57 



habit is a marked one. So much is this the case that paleontolo- 

 gists always suspect water habits in reptiles showing it, even though 

 but few parts of the skeleton are known. 



Increase in the number of bones of the digits is a more or less 

 conspicuous characteristic of all mosasaurs. In those forms in 



\\ \ I 







in 



"IV 



Fig. 74. — Clidastes; left front paddle: Fig. 75. — Tylosaurus; left front paddle: 



c, coracoid; //, humerus; r, radius; sc, c, coracoid; sc, scapula; //, humerus; r, 

 scapula; u, ulna. radius; u, ulna. 



which the wrists and ankle bones had become cartilaginous in great 

 part, as many as eleven phalanges have been observed in the longest 

 toes, though in other forms, those with more completely ossified 

 wrists and ankles, only two or three additional bones have been 

 developed in the longest fingers and toes by aquatic habits. The 



