212 



WATER REPTILES OF THE PAST AND PRESENT 



are very peculiar, and very different from the corresponding bones 

 of other crocodiles. While the spines of the tail bones along the 

 anterior part are only moderately stout and long, and are directed 



obliquely backward, near the 

 terminal part they become 

 suddenly much broader and 

 are directed upward, and, a 

 little farther along, obliquely 

 forward. The chevron bones 

 on the under side also here 

 become broader and longer. 

 The end of the tail curves 

 markedly downward to end 

 in a slender point. It will 

 be remembered that a similar 

 downward curvature of the 

 end of the tail observed in 

 nearly all specimens of ich- 

 thyosaurs induced in Owen 

 the belief that the animals 

 had a fleshy terminal fin, a 

 belief which later discoveries 

 of the carbonized remains of 

 the flesh confirmed. The 

 peculiar structures observed 

 in various specimens of these 

 sea-crocodiles, even though 

 no impressions or remains of 

 the fleshy parts have been 

 discovered, is quite con- 

 clusive evidence that these 

 animals also had a broad, 

 fleshy, terminal fin. No other explanation of the structure is 

 possible. 



The ribs are not at all stout and are not much curved. They 

 are directed posteriorly in the known specimens preserved in the 



^ ^ 



Fig. iio. — Geosaurus. Elongate hind leg, 

 and paddle-like front leg. (After Fraas.) 



