400 MR. ST. GEORGE MIVART AND DR. J. MVJRIE [June 26, 



thinner than that of the biceps) into the radial side of the shaft of 

 the ulna, lower than the insertion of the biceps, but higher than that 

 of the biceps in the Hare, Guinea-pig, and Rabbit. 



The second portion, which also exists in the Hare and Rabbit, is 

 much smaller in size, and has a separate origin and insertion. It 

 arises from the front of the shaft of the humerus, immediately within 

 the first part of the brachialis anticus, and below the deltoid ridge ; 

 it is a laterally compressed band of muscle, and has an insertion im- 

 mediately adjacent to and to the inner side of the first part. 



In the Rabbit the two portions of the brachialis anticus (which 

 are more equal in size than in D. cristata) are separated from each 

 other by the insertion of part of the pectoralis major, which runs far 

 down the humerus, this part in Dasijprocta being inserted between 

 the inner portion of the brachialis anticus and the biceps. 



In the Guinea-pigs examined by us there was no second and sepa- 

 rate portion to the brachialis anticus. 



The triceps consists of three heads as in Man, and with the usual 

 origin and insertions ; the scapular head is large, and, moreover, has 

 in addition a slight origin from the fascia investing the infraspinatus 

 muscle (figs. 2 & 3, T.). 



The other Rodents used for comparison do not vary from the above 

 description. 



The supinator longus, as Meckel observes, appears to be entirely 

 absent, unless the inner parts of the brachialis anticus be considered 

 a displaced supinator longus ; but such can hardly be the case, on 

 account of its very different insertion. 



The Guinea-pig resembles the Agouti in this respect. 



It is certainly wanting in the Hare. 



The supinator brevis has an origin from the annular ligament of 

 the radius, and is inserted as usual into the shaft of that bone 

 (fig. 3, 5. b.). 



It is present and similar in the Guinea-pig. 



In the Hamster, Agouti, Marmot, Beaver, and Rabbit, according 

 to Meckel*, it is inserted entirely, or almost so, into the upper half of 

 the radius. 



In the Hare and Rabbit we found it very small. 



The pronator radii teres (figs. 2 & 3, P. r. t.) arises from the in- 

 ternal condyle, and has an insertion into the middle of the shaft of 

 the radius as in the Hare, Rabbit, and Guinea-pig — not, however, 

 extending to the lower end of this bone, as Meckelf asserts is the 

 condition this muscle assumes in the Rodents. 



On the left fore limb of- the Agouti we did, however, notice a thin 

 fascia-like tendon, which seemed to spring from, or be a continuation 

 of, the pronator teres, and to run on as far as the carpus. 



The Jlexor carpii radialis has origin from the internal condyle, and 

 an insertion by a long tendon which passes to the groove inside the 

 styloid process of the radius, thence over the scaphoid, dipping deeply 

 beneath the short flexor muscles of the pollex, and ending in the base 

 of the first phalanx of the index (fig. 2,F.c.r.). It is similar in 

 the three Rodents examined for comparison. 



* Loc. cit. p. 30fi. t hoc dt. p. 300. 



