SAUROPTERYGIA ioi 



go back to their earlier condition. The nothosaurs do prove 

 beyond all possibility of doubt that the plesiosaurs were at least 

 the descendants of animals closely allied to them, so closely, indeed, 

 that it is doubtful whether we could distinguish external differences 

 were all of them actually living at the present time. 



We have repeatedly seen that all aquatic animals have some 

 or all the bones of the limbs shortened, and it is of interest to 

 observe that the early plesiosaurs had longer forearm and foreleg 

 bones than the later ones, just as we have seen was the case with the 

 early ichthyosaurs. It would seem probable that all the early 

 plesiosaurs had long necks, though some of the late ones in Cre- 

 taceous times had relatively short necks, shorter even than the 

 known nothosaurs possessed. 



The nothosaurs doubtless lived about the shores of the ancient 

 seas, spending much of their time in the water, leaving it perhaps 

 when hard pressed by their enemies, as do some modern reptiles, 

 or to rear their young. The teeth of the nothosaurs are long 

 and slender in front, shorter behind. The animals must therefore 

 have been carnivorous in habit, feeding probably upon such fishes 

 as they could catch, and the various invertebrates which live in 

 shallow water. The structure of the jaws and their attachments 

 are quite as in the plesiosaurs, proving that they could not have 

 swallowed large objects; but the skull is broader and flatter than 

 that of most plesiosaurs, indicating habits not unlike those of the 

 modern alligators and crocodiles. 



Some time we shall doubtless find remains of nothosaurs or 

 nearly allied animals elsewhere than in Europe, but probably not 

 from later deposits than the Triassic. So far as we now know, their 

 geological range and geographical distribution were much restricted; 

 they evidently wholly died out shortly after the plesiosaurs appeared 



