CACOPS ASPIDEPHORUS 269 



haekward to ojjten on the inner surface a little back of the border of 

 tlie subscapular fossa, in which the supracoracoid and the supraglenoid 

 foramina both open. The lower anterior part of the bone is thickened, 

 with truncate edges, and is convex in outline. The upper end of the 

 cartilagious border continues l)ackward as an angular thickening, nearl}^ 

 on a level with the upper border of the preglenoid facet. The thickening- 

 extends as a ridge a short distance backward. In much probability this 

 ridge limits the upper border of the epicoracoid, since in the immature 

 specimen already spoken of a sutural line seems to run directly backward 

 below the upper edge of the preglenoid facet, quite as in Varanosaurus. 

 The lower edge of the preglenoid facet continues as a rounded border 

 downward and forward part way to the lower margin of the bone. In 

 the cavity thus formed at the lower end of the facet is the opening of the 

 supracoracoid foramen. On the inner surface of the bone, near the 

 middle, extending downward subparallel with the anterior border of the 

 bone, is the anterior border of the subscapular fossa. In its middle part 

 the free border overhangs a deep fossa looking l^ackward, at the upper end 

 of which opens the supraglenoid foramen ; at the lower end is the opening 

 of the supracoracoid foramen. Back of this margin the bone is convex, 

 and is pierced by the inner opening of the glenoid foramen. 



Cleithrum. — The clei thrum, found in position on either side, is re- 

 markable for its large size. Its lower part is a long rod closely attached 

 to the anterior margin of the scapula as far as the angular thickening I 

 have described; it is overlapped through nearly its whole extent by the 

 upper part of the clavicle. The upper part of the cleithrum is broadly 

 dilated and thin, covering the upper border of the scapula to its hind 

 angle and arched inward. Its borders are very thin, convex above, con- 

 cave below ; the posterior thin margin is nearly straight. The bone above 

 forms a sort of roof, convex outwardly, concave inwardly. 



Clavicles. — The clavicles are small, somewhat spoonshaped, with curved 

 handle. The upper, slender part is closely applied to the outer, anterior 

 side of the lower, rodlike part of the cleithrum, reaching nearly to the 

 dilated portion. The lower end, curved inward and a little backward, is 

 dilated with thin margins, concave on the inner side where it articulates 

 with the interclavicle, convex on the exterior or lower surface. It under- 

 laps the interclavicle and partly covers the lower anterior border of the 

 epicoracoid. 



Interclavicle. — The interclavicle is a sniall, thin bone dilated and 

 thinned in front where it overlies the ends of the clavicles, which touch 

 in the middle. The posterior extension or "stem" is short, not as long as 

 the expanded part. 



XIX— Bull. Gpor.. goc. Am., Vol. 21, 1000 



