OP CREATION. 161 



to some purpose even on land, and in this respect 

 the Plesiosaur was indeed much better provided than 

 the seal. 



The extremities themselves do not differ very 

 greatly from those of some of the cetaceans, but 

 they were longer, more tapering, and seem to have 

 possessed greater flexibility. There are stout and 

 moderately long bones corresponding to the shoulder 

 and thigh bone, a couple of short and flat bones which 

 represent the bones of the fore-arm and the lower part 

 of the leg, and then a succession of bones, oblong and 

 flattened, and extending to some distance, which were 

 enclosed entirely within the skin during the life of 

 the animal, and which formed the solid part of the 

 paddle. 



There are several very distinct varieties of form 

 in the different species of Plesiosaurus, and amongst 

 them are some in which the head is far larger in 

 proportion, the neck shorter and thicker, and the 

 body more expanded. Others again are remarkable 

 for the large dimensions of the paddles ; and others 

 for different modifications of structure, but all agree 

 sufficiently in the principal character^, and teach us 

 with equal distinctness what were the general habits 

 of the animal. The specimens indicate also very 

 different sizes; but, since in all reptiles the limit of 

 growth is much less strongly determined, and the 

 increase much greater, than in more highly organized 

 animals, it will be sufficient to state that the largest 

 complete specimen yet found is about eighteen feet 

 in length, but that there are fragments of indivi- 

 duals which would seem to have been nearly twice as 

 large. 



