| OCR Text |
Show 166 MR. F. G. PARSONS ON T H E [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 Myoxus and Cricetus it was only inserted into the first four ribs. In Georychus the muscle came from the anterior four cervical vertebrae and was inserted into the first four ribs. In Bathyergus the arrangement w^as the same except that it reached the fifth rib. In Rhizomys, although there was no scalenus anticus, the scalene mass was Fig. 6. SER- MA.G. SCALENUS, ---SUBCLAVIAN ART * BRACK, PLEX. ..RECT. !EXT. OBL. 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 Eodents, the same four divisions of the pectoral mass which have already been denned l 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 j3, 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; 1 P. Z. S. 1894, p. 259. |
