28 FOSSIL REPTILES OF DORSET. 



HUMERUS Sp. 



Swanage. Nos. 2174 and 21979, British Museum. 

 A large series of fossil bones, mostly Ichthyosaurian and 

 Plesiosaurian from the Kimmericlge clay beds of Gillingham, have 

 been kindly deposited in the County Museum by our fellow 

 member, R. Ereame, Esq. Being almost entirely hidden in large 

 masses of hard stone, containing much pyrites, they cannot easily 

 be identified and relegated to their proper specific places. It will 

 require much care and skill to extricate them from the matrix, 

 which will be done when means and opportunity allow. 



GENUS PLIOSAURUS, Owen. 



This genus is closely allied to Plesiosaurus, but differs in its 

 enormous head and extremely short neck. It has a limited 

 vertical range in Great Britain, from the Oxford Clay to the 

 Portland Beds inclusive. Its remains, however, have been found 

 in the Cretaceous beds of North America. Detached portions only 

 of the skeleton have as yet been recovered. It can be identified 

 better by its trihedral-shaped tooth than by any other character, 

 so similar is it to Plesiosaurus. The cervical vertebrae increase 

 in breadth and depth as they recede from the head, and assume 

 the Plesiosaurian type. 



PLIOSAURUS GRANDIS, Owen. 



Crown of the teeth subtrihedral, the outer side smooth and 

 slightly convex with an elevated ridge at each border ; the other 

 two sides, which are not separated from each other by a ridge or 

 border, are also convex, having coarse longitudinal strise. A tooth 

 from Kimmeridge which I presented to the British Museum, the 

 cast of which is in our County Museum, is twelve inches long from 

 the point of the crown to the bottom of the dilated root, which is 

 unusually perfect, the absorbing effect of the successional tooth not 

 having commenced. Its gigantic dimensions give a good idea of 

 the size and destructive power of the jaw which contained it. 

 Besides the teeth the generic character of Pliosaurus is shown by 

 the vertebrae, which somewhat resemble those of Ichthyosaurus 



