CROCODILIA 21 s 



hardly probable. We may therefore infer that the thalattosu- 

 chians, while distinctively sea-reptiles, had not entirely lost their 

 land habits. Moreover, it is highly probable that their egg-laying 

 habits, which would hardly change with a greater adaptation to 

 water life, compelled the animals recurrently to visit the shores. 

 To have finally lost their hind legs they must have become vivip- 

 arous in habit, since it seems to be impossible for any true air- 

 breathers to be hatched in water. Perhaps this insurmountable 

 habit was the final cause of their extinction in competition with the 

 truly viviparous aquatic flesh-eaters. The thalattosuchians had 

 but a brief existence in geological history, during the latter part of 

 the Jurassic period only, so far as certainly known, nor did they 

 become widely dispersed over the earth; they are known from 

 Europe, possibly from Brazil. 



