THE GREAT SEA-LIZARDS 79 



of resemblance, in the backbone, ribs, and skull. Fig. 13 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 Eegis in Dorset, and Whitby 

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

 eight to ten feet in length. But in the rocks of the Cretaceous 

 period, which was later, are found larger specimens. There is 

 a cast of a very fine specimen from the Upper Lias on the 

 wall of the Geological Gallery No. IV., at South Kensington, 

 which is twenty-two feet long. But some of the Cretaceous 

 forms, both in Europe and America, attained a length of forty 

 feet, and had vertebrse six inches in diameter. The bodies of 

 the vertebrse, or "cup-bones," are either flat or slightly concave, 

 showing that the backbone as a whole was less flexible than in 

 the fish-lizards. 



Plate V. is from a photograph of a Plesiosaurus skeleton set up 

 as if it were that of a living animal in the Natural History 

 Museum, in 1892, the bones having been carefully collected by 

 Mr. Alfred N. Leeds, of Eyebury, who has disinterred the 

 separate bones of many distinct skeletons of Plesiosaurs from 

 Oxford Clay strata near Peterborough, and to whom great 

 credit is due for his laborious work. Quite recently another 

 big Plesiosaur skeleton has been mounted in the Natural 

 History Museum, near to the above. Though much disturbed 

 by crushing, it shows some remarkable and novel features. 



