168 MH. p. 6. PARSONS ON THE [Jan. 14, 



Deltoid. — This muscle in the Myomorpha has the usual three 

 parts, but the intervals between them are hardly noticeable ; more- 

 over, they are all inserted into the humerus at the same point. Tiie 

 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, Oeorychus, and Siphneus the intervals are so 

 ill-marked that the muscle appears single as in Man. 



Supraspinatus,Infraspinaius, and Subscapularis. — These resemble 

 the same muscles in the other liodents in having the human attach- 

 ments. In some, e.g. (7Wc«/omv«, 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-fourtlis 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 vi'hich that muscle is wrapped round the lower border of it. In 

 Myoxus, Oricehts, Bhizomys, Microtus, Mus harharus, and M. rattus 

 the teres major is wrapped round by the latissimus dorsi, so that 

 the latter is inserted anteriorly to it. - In Ci-icetomys, Georychus, 

 and Baihyergus the wrapping round is not so complete, and the 

 teres major is inserted in front of the latissimus dorsi. In Siph- 

 nevs 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, Ci-icetomys being the only animal in which it could be 

 described as well-marked. It is interesting to notice that a strong 



— Sup. SPIN. 



Sliouldei'-iniiscles of Wihomys. 



