348 



THE PORTLAND OOLITE PERIOD. 



CHAP. 



Length, 2-25 inches; breadth, 3-85 j height, 3-50 ; or, if length 

 = 100, breadth =171, height = 155. 



Bibs occur at Shotover, not rarely, but probably they do not 

 belong to this species. In the Market- Rasen specimen only frag- 

 ments are recognised, with enlarged proximal heads. 



A scapulo-clavicular bone, obtained at Shotover, which is in the 

 museum of the Earl of Enniskillen, belongs, according to Professor 

 Owen, to Pleiosaurus grandis. The bone is triradiate, the longest 

 measure being 9 inches. 



An ischium is mentioned by Professor Owen (1839) as having 

 been found at Shotover, measuring 13 inches along the medial 

 line, and 4 inches across the anterior edge. The inner margin is 

 formed on a very convex curve, so as not to touch the opposite bone, 

 except in the anterior part by a short symphysis. A bone cor- 

 responding to this was placed in the Museum in 1858. 



A coracoid of considerable size, in two fragments, from Fox- 

 combe, has been for several years in the Oxford Museum, and is 

 represented in Diagram CXLII. 



Diagram CXLII. Coracoids of Pleiosaurus. Scale one-tenth of nature. 



The bone is, in a general sense, plano-concave, thick anteriorly 

 and thin posteriorly, and smooth. The bones met with straight 

 and plane faces for a considerable length (6*5 inches), and then 

 diverged widely. The symphysis is so sloped that the bones met 

 at an angle of 140, so as to form a broad obtuse ridge, of great 

 strength. The humeral articulation, formed on a curve, is 6-2 

 inches long, by 3*1 deep ; the symphysial plane is 6-5 by 4-0. The 

 curve is slight from the articulation to the symphysis. Length 

 about 16-0 inches, breadth io'2. 



