378 THE PORTLAND OOLITE PERIOD. CHAP. 



the broad medial expansion, without oblique ridges, and without 

 keel at the symphysis, which is straight for a considerable length. 



Extreme breadth over the condyles, 16-0 inches; length along 

 the middle, 8-35 ; depth at the symphysis, 1-5. Articular faces 

 double, the two surfaces irregular and inclined to one another 

 about 90 ; the inner one 2-5 inches, the outer 3-0 long ; depth, 



2-25. 



A pair of coracoid bones from Shotover, much vaulted^ under the 

 broad expansion toward the symphysial line, which is much curved, 

 the two bones meeting only for a short length. 



Diagram CLXXIX. Coracoids of Plesiosaurus. 



Extreme breadth over the articulating faces of the pair, 22*0 

 inches ; length along the middle, 10-5 ; depth at the anterior part 

 of the symphysis, 2'Q ; articular faces formed on a continuous curve, 

 in length 5-0, in depth 2*25. 



The anterior part of the symphysis is nearly in a vertical plane ; 

 if the bones joined along it, the combined figure would be much 

 altered, by the advance of the articulating heads, and the formation 

 of an obtuse mesial ridge. 



A portion of a large ischial bone, formed on the same general 

 plan as that mentioned in connection with Plesiosaurus Oxoniensis 

 (Diagram CXVL), was placed in Dr. Buckland's Museum, when 

 it came under my management, with the remains of Pleiosaurus 

 brachydeirus from Market-Rasen. It was not labelled, and it is 

 not made certain by examination of the matrix that it came from 

 the same locality as the others. This is represented in Diagram 

 CLXXX. 



The strong obtuse ridge which runs from the articular prominence 

 toward the retral margin separates two broad surfaces, which are 

 inclined to one another 125, so that the space under the ridge 



