74 REPORT -1839. 



the radius, and resembles both in this proportion and in its 

 tshape that of the PL dolichodeirus : its radial or anterior con- 

 cavity is less deep, and the posterior margin less convex than 

 in the PL Haivkinsii or PL ynacrocephalus. 



Inches. Lines. 



The length of the ulna is 3 6 



The breadth 2 2 



The femur differs in form as well as in size from the humerus : 

 its anterior as vrell as posterior margin is slightly concave ', and 

 it is upon the whole somewhat shorter and thicker in propor- 

 tion to its length. Near the proximal extremity there is a rough 

 muscular protuberance corresponding with that in the humerus, 

 but more circumscribed and more raised. The distal end is 

 bounded by a pretty regular convex curve, and its rough arti - 

 cular surface is in the form of a compressed ellipse, not en- 

 croached upon by any depression as in the humerus. 



Inches. Lines. 



Length of the femur 7 8 



Breadth of its distal end 3 6 



The tibia like the femur is thicker as well as shorter than 

 the corresponding bone in the fore-arm. 



Inches. Lines. 



Length 3 



Breadth of the proximal end ... 2 3 

 distal end 1 7 



The remaining bones of the extremity are not sufficient in 

 number to enable me to recompose the entire extremity so as 

 to compare together the bones of the hand and foot : but the 

 proportions above described of the larger bones of the anterior 

 extremities are sufficient to distinguish the present from any 

 other known species of Plesiosaur. The only doubt which oc- 

 curred was with reference to the fact of the humerus and femur 

 having actually belonged to the same skeleton ; but the corre • 

 spondence of the bones in texture, colour and general appear- 

 ance, and in the rough surfaces for muscular attachment, coin- 

 ciding with the evidence of the indefatigable and acute discoverer. 

 Miss Anning, as to the proximity of all the remains of this 

 specimen in the lias matrix, assured me that the comparison 

 might be safely made. 



Plesiosaurus pachyomus. 



A new species oi Plesiosaurus is indicated by certain remains, 

 in the collection of Prof. Sedgwick, from the greensand of 

 Reach about six miles from Cambridge. 



