135 



surface concave externally, prodiiced by the action of the thigh. 

 The sterno-costal bones are seven in number : the Jast one curved 

 suddenly at its costai end. 



•' The body of the sternum is long. The keel is much developed 

 at its top, and forms a very acute angle posteriorly, terminated by 

 a small line. The space for the attachmenc of the middle pectorai 

 musele is considerably larger than that for the attachment of the 

 great pectorai. On each side of the keel there is a large space, ter- 

 minating inferiorly in one, owing to the shortness of the middle 

 layer compared with the lateral ones. The keel terminates abruptly 

 inferiorly, The ensiform process has a ridge in the middle, along 

 which and the inferior edge of the keel a membrane \vas attached 

 (vvhich separated in maceration). The external layers of the bone 

 are, as has been already incidentally noticed, much longer than the 

 middle one: tliey curve inwards tovvard each other, and are tipped 

 with cartilage. The sterna.\fossa is large and very distinct. The 

 sternal apophyses are very large. 



" The coracoid bones are long, strongly forraed, and smooth an- 

 teriorly ; the margin much produced at the superior internai edge, 

 and the ends furnished with long hamuliform processes, extending 

 upvvards and downwards. The superior one is attached to the cla- 

 vicle by the intervention of ligament. The upper part of the os 

 coracoides is bent upon itself at an angle greater than a right ano-le. 

 They are larger at their inferior ends, the inner ends being p^ro- 

 duced and curved for^ards. The gienoid cavity of the bone is 

 situated on the exterior posterior part, and is formed by this bone 

 and the scapula, about three fifths of the cavity being formed by the 

 os coracoides. 



" Each clavicle is turned downwards, and is broader near the 

 coracoid bone, and tapering to the front, where there is a protu- 

 berance formed by the junction of the clavicles : this protuberance 

 does not touch the sternum. Posteriorly they give off a flat conical 

 process, which goes dovvn internally to the coracoid bone, and is 

 united to the process situated on the posterior part of the scapula 

 immediately inferior to its head. ' 



" The scapida is remarkably broad and thin : its neck and head 

 rounded. 'J'here are three articulating processes in this bone : one 

 wuh the furculum ; another with the coracoid bone; and the third 

 with the humeriis. 



" On comparing the sternum and adjacent bones vvith the sterna 

 oi some nearly allied Birds, we find less development of the keel 

 m the Loon, and less development of the lateral win<^s in the 

 Auk and more in the Sphenisais. The difFerences will be best shown 

 by the follovving tables : 



