BRITISH FOSSIL REPTILES. 83 



The bodies of the vertebrae are relatively longer than in the 

 PL Hawkinsii, being intermediate in this respect between it 

 and the PI. dolichodeirus . 



Localities. — ^The vertebras of this species occur in the lias at 

 Lyme Regis, in that of the Aust Cliff, Bristol, and in the 

 neighbourhood of Whitby. 



Plesiosaurus grandis. 



From the greensand, Kimmeridge clay, and Oxford clay, 

 many specimens have been obtained of humeri or femora, 

 closely corresponding with the Plesiosaurian type of these 

 bones, but of gigantic size, and belonging to two distinct spe- 

 cies of Enaliosaurian reptiles. 



The long bone (humerus or femur) indicative of the first of 

 these species, presents the ordinary rough, elliptical, slightly 

 convex head, beneath which the bone slightly contracts to 

 about one third of the distance from the opposite end ; it then 

 begins gradually to expand in breadth, and to decrease in 

 thickness to the distal extremity, which is terminated by a 

 pretty regular semicircular contour. The anterior margin is 

 slightly concave ; the posterior one more concave. Beneath 

 the head or proximal end of the bone there is a rough surface 

 for muscular attachment, but no process or trochanterian pro- 

 minence. The length of one of these bones in the collection of 

 Viscount Cole is sixteen and a half inches. The breadth of the 

 narrowest part of the bone is three inches and two thirds, that of 

 the broadest part eight inches. The surface of the upper third of 

 the bone is roughened with small perforations and longitudinal 

 ridges ; the surface of the lower two thirds is smooth, except 

 near the articular expanded extremity, which is pitted with 

 small vascular grooves. 



A second long bone in the same collection, having similar 

 characters to the preceding, measures fourteen inches in length, 

 seven inches in breadth across the distal extremity, and nine 

 inches in girth round the middle of the bone : this is probably 

 the humerus. 



A third long bone, also in the collection of Viscount Cole 

 and from the Kimmeridge clay at Shotover, belonging to the 

 same species as the preceding bones, measures seventeen inches 

 and a half in length, seven inches and one third across the 

 distal end, and nine inches in girth. The contour of the distal 

 articular end is rounded as in the first-described bone, and it is 

 probable that they are both femora ; but as the proportions of 

 the humerus and femur are not constant in the genus Plesio- 

 saurus, the nature of the above-described bones cannot be 



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