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Show 168 MR. F. G. PARSONS O N T H E [Jan. 14, Deltoid.-This muscle in the Myomorpha has the usual three parts, but the intervals between them are hardly noticeable; moreover, they are all inserted into the humerus at the same point. The portion rising from the spine of the scapula, instead of being the smallest, as in the Hystricomorpha, is usually the largest. This description applies to all the animals examined, with the exception that in Bathyergus, Georychus, and Siphneus the intervals are so ill-marked that the muscle appears single as in Man. Supraspinatus,Infraspinatus, and Subscapidaris.-These resemble the same muscles in the other Rodents in having the human attachments. In some, e. g. Cricetomys, the supraspinatus is larger than the infraspinatus ; but, as a rule, the reverse is the case. Milne- Edwards points out that in Siphneus the supraspinatus only occupies the anterior three-fourths of the fossa, the posterior part giving attachment to the rhomboid. Teres Major.-This has the usual attachments, its relation to the tendon of the latissimus dorsi is variable, and depends on the extent to which that muscle is wrapped round the lower border of it. In Myoxus, Cricetus, Rhizomys, Microtus, Mus barbarus, and M. rattus the teres major is wrapped round by the latissimus dorsi, so that the latter is inserted anteriorly to it. In Cricetomys, Georychus, and Bathyergus the wrapping round is not so complete, and the teres major is inserted in front of the latissimus dorsi. In Siphneus the arrangement seems to be the same. Teres Minor.-This muscle closely agrees with the description given of it in the other Eodents. It is very rarely a distinct muscle, Cricetomys being the only animal in which it could be described as well-marked. It is interesting to notice that a strong Fig. 7. Shoulder-muscle! of Rhisomys. |
