256 



THE SHOULDER GIRDLE. 



[CHAP. 



The postcapular fossa is very concave, and the subscapular 

 fossa convex. The Gangetic Fresh-water Dolphin (Platanista) 

 has a flat flabelliform scapula, with the prescapular fossa 

 entirely absent, and the acromion placed on the anterior 

 edge, the spine and the coracoid border having coalesced. 



Among the Whalebone Whales, Balcznoptera has a broad 

 fan-shaped scapula, like that of the true Dolphins, with long 

 parallel acromion and coracoid processes, and a suprascapular 



CL 



(I 



'f 



IG. 80. Right scapula of Dolphin (Delphimts tursio), \. gc glenoid cavity ; 

 a acromion ; c coracoid ; ff postscapular fossa ; af prescapular fossa. 



border which remains permanently in a cartilaginous con- 

 dition. In the Right Whales (Balcend) the scapula is more 

 massive and not so broad, and the coracoid is much reduced. 

 In Megaptera the scapula is triangular, and neither the 

 coracoid nor the acromion forms a distinct process. 



None of the Cetacea possess clavicles. 



The scapula of the SIRENIA is formed on quite a different 

 plan, being rather like that of the Seals in shape, narrow, 

 and curved backwards. The anterior fossa is nearly as 

 large as the posterior. The spine is moderately developed, 



