SHOULDER BLADE AND LOCOMOTION 



37 



the spine, the prescapular lamina, is most extensively developed in 

 such animals as per- 

 form complex move- 

 ments with the 

 Sea 



scapula of Dolphin (Tursiops tursio). 

 x . a, Acromion ; of, prescapular fossa ; c, cora- 

 coid ; gc, glenoid cavity ; pf, postscapular fossa. 

 (From Flower's Osteology.) 



fore- 

 limbs. The Sea Lion 

 and the Great Anteater 

 are cited by Professor 

 G. B. Howes as ex- 

 amples of this pre- 

 ponderance of the an- 

 terior portion of the 

 scapula over that which 

 lies behind the spine. 

 The general shape of 

 the scapula varies con- 

 siderably among the 

 different orders of mammals ; but it always presents the characters 



mentioned, which are nowhere seen 

 among the Sauropsida except among 

 certain Anomodonts, which will be 

 duly referred to (see p. 90). The 

 most conspicuous divergences from 

 the normal are to be found in the 

 Cetacea and the Monotremata. In 

 the former the acromion is approxi- 

 mated so nearly to the anterior 

 border of the blade-bone that the 

 prescapular fossa is reduced to a 

 very small area ; and in Platanista 

 the acromion actually coincides 

 . with the anterior border, so that 



FIG. 28. Side view of right half of 



shoulder girdle of a young Echidna that fossa actually disappears. In 



the Whales, too, the scapula is as 

 rule very broad, especially above ; 

 has frequently a fan-like contour. 



pf 



(Echidna hystrix). x f . a, Acro- 

 mion ; c, coracoid ; cb, coracoid 



border ; d, clavicle ; ess, coraco- a rule very broad, especially above ; 



scapular suture ; ec, epicoracoid ; 

 gb, glenoid border ; gc, 



In the Monotremata the acromion 



glenoid border ; gc, glenoid 

 cavity ; ic, interclavicle ; pf, post- 

 scapular fossa ; ps, presternum ; s, 

 spine ; ss, suprascapular epiphysis ; 

 ssf, subscapular fossa. (From 

 Flower's Osteology.} 



also coincides with the anterior 

 border of the scapula ; but the 

 sameness of appearance which it 

 thus presents (in this feature) to the Cetacean scapula is appar- 



