166 MR. F, G. PARSONS ON THE (Jan. 14, 
the first four or five ribs. In Cricetomys, Gerbillus, Microtus, Mus 
rattus, Myodes, and Heteromys the muscle rose from all the cervical 
vertebrae and was inserted into the first five ribs. In Myowus and 
Cricetus it was only inserted into the first four ribs. In Geory- 
chus the muscle came from the anterior four cervical vertebre and 
was inserted into the first four ribs. In Bathyergus the arrange- 
ment was the same except that it reached the fifth rib. In Lthizomys, 
although there was no scalenus anticus, the scalene mass was 
Fig. 6. 
‘; ei SCALENUS, 
O..- SUBGLAVIAN 
ART x BRAGH, PLEX. 
Scalene muscles of Rhizomys. 
divisible into an anterior and a posterior part: the anterior part 
rose from the second to the seventh 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. 
Muscles of the Anterior Extremity. 
The Pectoral Muscles—For purposes ‘of description, and for 
comparison with other Rodents, 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 Myoaus closely 
agrees, a rises from the anterior part of the sternum and runs 
horizontally outward to be inserted into the pectoral ridge ; 
1 P. Z. S. 1894, p. 259. 
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