OPHTHALMOSAUEUS ICENICUS. 63 



specimens to a single species, while at the same time admitting that future investigation 

 may render possible the diagnosis of others. 



Form. & Log. — Oxford Clay : England. 



All the following specimens from the Leeds Collection were obtained from the 

 Oxford Clay in the neighbourhood of Peterborough. 



R. 2133 (Leeds Coll. 62). Imperfect skeleton, including the shoulder-girdle described and figured by 

 Prof. Seeley in the Quart. Journ. Geol. Soc. vol. xxx. (1874) pp. 696-707, pis. xlv. & 

 xlvi. figs. 1-2, as the type of the genus and species. The portions o£ the skeleton 

 preserved include : the basioccipital (PI. I. figs. 13, 14), both quadrates (PI. I. fig. llj 

 with portion of the squamosal attached, right and left stapes (PL I. fig. 12), left 

 opisthotic (PL I. fig. 15), left parietal, and several other fragments of the skull ; some 

 sclerotic plates ; the posterior portion of the left ramus of the mandible ; a considerable 

 portion of the vertebral column (text-fig. 26), including the atlas, axis, and thirty-five 

 other precaudal vertebrae, together with twenty-one caudals mostly from the anterior 

 part of the tail; a number of separated and imperfect neural arches and many fragments 

 of ribs ; the shoulder-girdle, of which only the right scapula (figured loc. cit. supra^ 

 pi. xlv. fig. 2) and part of the clavicular arch (pi. xlvi. figs. 1-2) are of normal shape, the 

 other bones being deformed ; fourteen carpals and phalanges. The left scapula is an 

 almost shapeless mass of irregular bone fused with the upper end of the clavicle, and 

 the right coracoid (figured loc. cit. supra, pi. xlv. fig. 1) has a deep notch on its posterior 

 border, which is not present in normal specimens. 

 Dimensions (in centimetres) : — 



Basioccipital : total length 7'5 ; length of neural surface 5*1 ; greatest width 9 ; 

 width of condyle 6*7 ; depth of condyle 5'8. 



In this specimen the central portion of the condyle is much more convex than 

 the lateral portion. 

 Quadrate : extreme height 13 ; width of neck 6*3 app. ; width of articular surface 

 5-2 : length of ditto 7-6. 



„ , Atlas and Cervical 



Vertewa:. ^^^.j^^ (about the 5th). 



Height of centrum 7-2 (?) 6-9 



Width of centrum 7-4 7-3 



Length of centrum (measured at neural canal) . 4-5 3-8 



Greatest width with diapophyses 8-3 8-6 



The total length of the precaudal portion of the column, as preserved in this specimen, 

 is about 1'60 metres, but probably some vertebraj are wanting. 



Scapula : greatest length 2o-0 



width of proximal expansion 16'5 



blade (at narrowest) 4-6 



Coracoid : width iO-T 



length 21-S 



Posterior 

 dorsal. 



First 

 caudal. 



8-2 



S-2 



9-8 



9-6 



4-4 



4-1 



10-5 



9-3 



