82 REPORT — 1839. 



From the analogy of otlier Plesiosauri I should conceive the 

 femur to have corresponded with the humerus in the peculiar 

 form above described ; but as yet I have not met with an ex- 

 ample of this bone. 



Localities. — This bone was from the Kimmeridge clay at 

 Shotover, near Oxford. 



In the collection of Professor Sedgwick, at Cambridge, there 

 is an imperfect gigantic paddle, of which the first bone (whether 

 humerus or femur is not determinable in its detached condition,) 

 presents an expansion of the distal extremity hardly less dispro- 

 portionate than that above described : the length of this bone is 

 sixteen inches, the breadth of the distal extremity is eleven 

 inches. There are ten of the smaller bones of the paddle asso- 

 ciated with the above, and presenting the Plesiosaurian type, 

 but without modifications worthy of being specified. The spe- 

 cimen was discovered by Captain Smith in the Oxford clay 

 near Bedford. 



Plesiosaurus rugosus. 



In three museums, viz. that of Bristol, of York, and of Vis- 

 count Cole, I have observed Plesiosaurian vertebrae which are 

 readily distinguishable from all other vertebrae by the peculiarly 

 rugous character of the free or non-articular surfaces of the 

 body. But this superficial modification is not the only cha- 

 racter by which these vertebrae may be distinguished. 



The most characteristic vertebrae, viz. those from the middle 

 of the cervical region, although they present modifications of 

 the neurapophyses and costal articular surfaces resembling 

 those characteristics of the PL Hawkinsii more nearly than 

 any other species, yet differ therefrom in the following parti- 

 culars. The two costal impressions on each side are com- 

 pletely divided, and by a wider and a deeper groove : they are 

 situated nearer the lower margin of the vertebra ; and an extent 

 of surface equal to twice the vertical diameter of the combined 

 surfaces intervenes between them and the base of the neurapo- 

 physis. This is bounded by a more open angle than in the 

 PL Hawkinsii. The distance from the lower margin of the 

 neurapophysis to the articular surface of the posterior oblique 

 process, is only a little more than half the extent of the centrum 

 below the neurapophysis, a proportion which I have not yet 

 met with in any other species, but to which the vertebrae in 

 the PL Haivkiiisii offer the nearest approach. 



The contour of the articular surface of the vertebral body is 

 almost circular : the peripheral border of this surface is convex, 

 which leads inwards to a concavity, and the centre of the sur- 

 face again rises in a slightly convex form. 



