54 EXTINCT MONSTERS. 



and fingers were modified into little many-sided bodies, and so 

 articulated together as to make the whole limb, or paddle, a solid 

 yet flexible structure. In the long-necked sea-lizard, however, we 

 find a long arm-bone with a club-like shape ; and the two bones 

 of the fore-arm are seen to be longer than in the fish-lizard. But 

 a still greater difference shows itself in the bones of the finger, as 

 we look at a fossilised skeleton (or a drawing of one) ; for the 

 fingers are long and slender, like those of ordinary reptiles. 



There are only five fingers, and each finger is quite distinct from 

 the others. This is the reason why the Plesiosaur was considered 

 to depart less from the type of an ordinary reptile, and so re- 

 ceived its name. Other remarkable differences present themselves 

 in the shoulders and haunches, but these need not be considered 

 here. The species shown in Fig. 8 had rather a large head. 

 It is obvious that such a long slender neck as these creatures 

 had could not have supported a large head, like that of the fish- 

 lizard. Consequently, we find a striking contrast in the skulls of 

 the two forms. That of the Plesiosaur was short and stout, and 

 therefore such as could easily be supported, as well as rapidly 

 moved about by the long slender neck. Thus we find another 

 simple illustration of the " law of correlation," alluded to on 

 p. 6. The teeth were set in distinct sockets, as they are in 

 crocodiles, to which animals there are also points of resemblance, 

 in the backbone, ribs, and skull. Fig. 7 shows three different 

 types of lower jaws of Plesiosaurs. The one marked C belongs 

 to Plesiosaurus dolichodirus, the species represented in our plate. 

 There were no bony plates in the eye. Professor Owen thinks 

 that they were long-lived. The skin was probably smooth, like 

 that of a porpoise. 



The visitor to the geological collection at South Kensington 

 will find a splendid series of the fossilised remains of long-necked 

 sea-lizards. They were mostly obtained from the Lias formation 

 of Street in Somersetshire, Lyme-Regis in Dorset, and Whitby 

 in Yorkshire. Those from the Lias are mostly small, about eight 



