THE SKELETON IN MAMMALIA. PECTORAL GIRDLE. 495 



overhanging spine, and there is a second strong ridge running 

 along the proximal part of the glenoid border. 



The shoulder girdle of the EDENTATA shows some very 

 curious variations. In Orycteropus the scapula is of very 

 normal form and the clavicle is well developed. In the Pan- 

 golins and Anteaters the scapula is very broad and rounded ; 

 there is no clavicle in the Pangolins, and generally only a 

 vestigial one in Anteaters. In Armadillos, Sloths, and Mega- 

 theriidae, the acromion is very long and the clavicle is well 

 developed. In the Sloths, Megatherium, and Myrmecophaga, a 

 connection is formed between the coracoid, which is unusually 

 large, and the coracoid border of the scapula, converting the 

 coraco-scapula notch into a foramen. In Bradypus the 

 clavicle is very small, and is attached to the coracoid, which 

 sometimes forms a distinct bone 1 . 



In the SIRENIA the scapula is somewhat narrow and curved 

 backwards : the spine, acromion, and coracoid process are 

 moderately developed, and there is no clavicle. 



CETACEA. In nearly all the Odontoceti the scapula is 

 broad and somewhat fan-shaped ; the prescapular fossa is much 

 reduced, and the acromion and coracoid process form flattened 

 processes, extending forwards nearly parallel to one another. 

 Some of the Mystacoceti, such as Halaenoptera, have a broad, 

 fan-shaped scapula, with a long acromion and coracoid process, 

 extending parallel to one another. Others, such as Balaena, 

 have a higher and narrower scapula, with a smaller coracoid 

 process. 



In UNGULATA the scapula is always high and rather narrow, 

 and neither acromion nor coracoid process is ever much deve- 

 loped. In no adult Ungulate except Typotherium is there any 

 trace of a clavicle, but a vestigial clavicle has been described 

 in early embryos of sheep 2 . 



UNGULATA VERA. In the Ruminantia the suprascapular 



1 See R. Lydekker, P. Z. S. 1895, p. 172. 



2 See H. Wincza, Morph. Jahr. xvi. p. 647, 1890. 



