56 



MAEINE EEPTILES OF THE OXFOED CLAY. 



strongly convex anterior and internal border ; the thin posterior edge is concave and 

 forms the anterior border of the coraco-scapular foramen, if that opening was really 

 enclosed internally by the meeting of the scapula and coracoid. The ventral rami of 

 the scapttlse, in any case, may have met each other in the middle line, but seem to have 

 been separated by the triangular interclavicle (int.cl.). This bone (text-fig. 22) is 

 gently convex below and concave above from side to side, and very slightly convex from 

 before backwards on the ventral surface. The anterior border (f.b.), which has a thin 

 smooth edge, is concave from side to side. The lateral border (Lb.) is at first a little 

 concave, then posteriorly convex, the bone terminating posteriorly in a stout, blunt, 

 asymmetrically placed process (p.p.). On the visceral surface the lateral borders are 

 bevelled away and roughened, evidently for union with some other element, and this 



Interclavicle of Peloneustes pliilarchus : A, dorsal (or visceral) surface; B, ventral surface. 



(E. 2442, | nat. size.) 



f.b., front border; l.b., lateral border ; p.p., posterior process. 



bevelled surface extends the whole length of the lateral border. The inner edge of 

 the ventral ramus of the scapula cannot well have united with the whole border, and 

 so it seems possible that some lateral elements (clavicles) were present, though they 

 have never yet been found. In any case, there seems little doubt but that this 

 triangular bone must be regarded as the interclavicle, and it has been so described and 

 figured by Seeley *. Lydekker f, on the other hand, regarded it as an omosternum. 



* Seeley, "Shoulder-girdle and Clavicular Arch in Sauropterygia," Proc. Eoy. Soc. vol. li. (1892) p. 131, 

 fig. 4. 



t Catal. Foss. Eept. Brit. Mus. pt. ii. (1889) p. 151, fig. 44. 



