1894.] myology or BODEXTS. 263 



In the Caviidae the arrangement is the same as in Ccelogenys 

 (C cobaya, Ceredon rwpestris). 



Teres Minor. — The teres minor rises from the humeral third to 

 half of the axillary border of the scapula, and is inserted just 

 below the insertion o£ the infraspinatus. It is sometimes a 

 perfectly distinct muscle, but iu most cases is so closely united 

 to the infraspinatus that, were it not for its being supplied by the 

 circumflex nerve, it would be most conveniently described with 

 that muscle. The teres minor was seen most ^ distinctly in 

 Lagostomiis, in which animal a fibrous band was found running 

 from the metacromial process to the origin of the long head of 

 the triceps, covering the infraspinatus and teres minor near 

 their insertions. 



In the Sciuromorpha the muscle is specially indistinct. 



Biceps Cubiti.— The biceps always rises by a strong tendon from 

 the margin of the glenoid cavity at the base of the coracoid process ; 

 it may or may not have a second head rising from the tip of that 

 process, or from the surface of the coraco-brachialis. Its insertion 

 is into the radius, ulna, or both bones just below the sigmoid 

 cavity, occasionally, however, it is prolonged farther down the 

 bones. The semilunar fascia from the inner side of its tendon 

 to the fascia of the forearm is very indistinct, but by careful 

 dissection a few fibres may be traced. 



In the Dipodidae there is only one head, and the insertion is 

 almost entirely into the ulna (Dipus a=gyptiiis, Alectaga indiccc). 



In the Octodontidse there are two heads ; the insertion is into 

 both radius and ulna (Myopotamiis, Aidacodv.s, Capromys, Octodon). 



In the Hystricidas there is only one head in Hystrix, but two 

 in Sphingurus and Erethizon dorsatus ! ; it is inserted largely into 

 the radius in the Tree-Porcupines, but chiefly into the ulna in 

 Hystrix. 



In the Chinchillidae there are two heads ; the insertion is into 

 the coronoid process of the ulna and the oblique line of the radius 

 (OhinchiUa, Lagostomiis). In the Viscacha I dissected there were 

 three heads to the biceps on the left side, the extra one rising 

 from the front of the great tuberosity of the humerus. 



In the Dasyproctidae there is only one head, and the insertion 

 is entirely into the ulna (Dasyprocta, Ccelogenys). 



In the Caviidae the arrangement is the same as that in the 

 Dasyproctidae (Cavia cobaya, Ceredon rupestris, Dolichotis 2 ). In 

 the Sciuromorpha, Sciurvs, Pteromys, Arctomys, and Xerus have 

 the muscle rising chiefly by the glenoid or long head, but also by 

 some fibres from the front of the coraco-brachialis (representing 

 a short head). The insertion is almost entirely into the tubercle 

 of the radius so as to act as a supinator. 8permop>hilus differs 

 in 1 ho absence of the short head. Castor has only one head and 

 the insertion is entirely into the ulna. 



Coraco-brachialis. — The three parts of this muscle described b) r 



1 Mivart, P. Z. S. 1882, p. 271. 



2 Beddard, P. Z. S. 1891, p. 236. 



18* 



