1896.] MTOLOOY OF KODENTS. 169 



ligament was seen in Rliizomys running from the axillary border 

 of the scapula, between the origins of the teres major and minor, 

 across the latter muscle to the metacromioii process. A similar 

 ligament has already been described in Lagostomus '. 



Biceps Ciibiti. — There can be no doubt that, spealting generally, 

 one of the characteristics of the Myomorpha is a double-headed 

 biceps. This was noticed in every specimen which I dissected. 

 Milne-Edwards, however, found only one head in Siphneiis, but it 

 is possible that further investigation may prove that this was 

 merely an individual variation. In Ilydromys Windle does nob 

 notice the condition of the biceps. 



As a rule the insertion is into both bones of the forearm, but in 

 Cricetus and Myoxus the muscle only goes to the radius, while in 

 lihizomys the ulna is the only bone to which it is attached. In 

 Georychus and Bathyergus the two heads are easily separable 

 down to the insertion by a little force. In the former the coracoid 

 head goes entirely to the radius, the glenoid head to the radius 

 and ulna ; in the latter both heads can be traced to both bones. 



Coraco-hrachialis, — In the Myomorpha the most usual arrange- 

 ment is to find the second and third parts, described by Wood*, 

 present ; they are, however, fused, and the muscle has one 

 continuous insertion from the middle of the humerus to the 

 internal condyle. This description applies to lihizomys, Siphneus, 

 Microtus, Myodes, Heteromys, Hydromys, and the MurinsB. Q'he 

 Cricetinse {Cricetiis and Cricetomys) have the same arrangement, 

 but in addition the first part or rotator humeri is present. In 

 Gerhillus and Myoxus only 'the second part was seen. 



In Qeoryclms the muscle was absent, while in Bathyergus it 

 was very small, and was only represented by the second part. 

 Milne-Edwards says that the muscle is absent in " le Kat-Taupe 

 du Cap," by which, I suppose, Bathyergus is meant. In all the 

 animals dissected, as in other Rodents, the musculo-cutaneous 

 nerve passes above the second part of the muscle. 



Brachialis Anticus. — All the Myomorpha have the external and 

 internal heads of the brachialis anticus, and these are more or 

 less completely fused ; perhaps Bathyergus shows them most 

 clearly separated from one another. The insertion, in every case 

 that I dissected, was into the ulna only, but Milne-Edwards 

 describes an additional feeble attachment into the head of the 

 radius in Siphneus. 



Triceps and Anconeus. — There is no difference between the 

 Myomorphine triceps and that of other Eodents. In Cricetomys 

 it was noticed that the outer head was inserted largely into the 

 fascia oE the outer side of the forearm. Bathyergus resembles 

 Castor in the great development of tlie muscle, and in the fact 

 that it is attached to both sides of the olecranon, as well as to the 

 lop. The anconeus has the usual attachments, and shows nothing 

 of special interest. 



' P. Z. S. 1894, p. 263. 



' Journ. of Anat. vol. i. p. 45, 



