ICG 



Mil. r. G. I'ABSONS ON TUB 



[Jan. 14, 



the first four or five ribs. lu C'ricetomys, Oerhillus, MIcrohts, Hus 

 ruttus, Myodes, and Heteromys the muscle rose from all the cervical 

 vertebrffi and was inserted into the first five ribs. In Myoxus and 

 Cricetus it was only inserted into the first four ribs. Tn Ocory- 

 ehus the muscle came from the anterior four cervical vertebraj and 

 was inserted into the first four ribs. In Bathyerytts the arrange- 

 ment was the same except that it reached the fifth rib. In BMzomys, 

 although there was no scalenus anticus, the scalene mass was 



Fig. 6. 



.SER.MJkC. 



I'. Scalenus, 



I 



;t---SUBCLAVIftM 



ARTsBRACH.PLEX. 



lEXT. OBL. 

 Scalene muaolea of Bhhomys. 



divisible into an anterior and a posterior part : the anterior part 

 rose from the second to the seyfenth cervical transverse processes 

 and was inserted into the first rib, while the posterior part only 

 came from the transverse process of the atlas and went to the first 

 four ribs. 



Mtiscles of the Anterior Extremity. 

 The Pectoral Muscles. — For purposes of description, and for 

 comparison with other liodents, the same four divisions of the pec- 

 toral mass which have already been defined ' will be here adhered 

 to. The chief differences noticed in the Myomorpha are that a is 

 not so oblique a muscle, and, as its fibres correspond in direction 

 with those of /3, the two parts are much less easily distinguished 

 from one another. In Cricetomys, with which Myoxus closely 

 agrees, a rises from the anterior part of the sternum and runs 

 horizontally outward to be inserted into the pectoral ridge ; 

 ' P. Z. S. 1894, p. 259. 



