1896.] MYOLOaX of EODBIfTS. 173 



Iti no case could I satisfy myself of the existeacs of an adductor 

 or opponens poUicis. 



Miiscle.1 of the Little Finger. — These are not so easily made out 

 as in the other itodents. The abdactor is present, but is not 

 double. The flexor brevis is represented by the ulnar slip of the 

 interosseus muscle to the little fiager, when there happens to be a 

 muscle in that position. I have never been able to find an 

 opponens, although Windle describes it in Uydroynys. 



Iiiterossei. — In all the animals examined, except Oeorijchus and 

 Bathyerfjus, there were eight interossei, the inner of whicli formed 

 the Hexor brevis minimi digiti. In these two animals there were 

 no interossei attached to the fifth finger, although the two 

 sesamoid bones supposed to be developed in them were present. 

 Practically the same arrangement was found in the Beaver. In 

 Cricetomys, MicrotMs, and possibly in Oricetiis, there was an ■ 

 adductor minimi digiti, which recalls the figure already published ' 

 of the same muscle in Gcelogenys. In Rhizomys and Gerbillus 

 there is an adductor indicis. These two muscles are situated on 

 a plane superficial to that of the interossei, and I have not come 

 across any Myomorphine animal which ])osgesse3 hotb of thera, 

 although they frequently co-exist in the liystricomorpha. 



Muscles of the Trunk. 



Pannicidus Oar}iosus. — In the majority of the Myomorpha the 

 panniculus corresponds to the rodent type already described. 

 The sterno-facialis is always present, but seldom large. In 

 Gcorychus and Bathyergus the panniculus, especially the anterior 

 part, is very well developed; iu the former the platysma is 

 very strong and rises from the angle of the mouth and from the 

 median raphe running back from the symphysis menti, it runs 

 backward and upward to be lost over the region of the shoulders, 

 though some of the more posterior fibres are attached to the 

 raetacromial process. When this is removed, the whole length 

 of the sterno-facialis and epitrochleo-facialis comes into view, 

 the former rising from the posterior half of the sternum, the 

 latter from the internal condyle of the humerus ; they both run 

 forward to be inserted into the fascia on the surface of tlie 

 masseter. In Bathyergus the sterno-facialis has undergone greater 

 development, and is continuous posteriorly with tlie panniculus 

 of the abdomen ; this I have figured, and have pointed out' that it 

 is a possible foreshadowing of the human sternalis muscle. The 

 posterior part of the panniculus in Bathyergus is also well marked, 

 and gets an attachment to the external tuberosity of the tibia and 

 to the ramus of the ischium. In Heteromys among the Georayidas, 

 the pouch causes a good deal of modification in the facial 

 panniculus. The superficial part or platysma rises from the 



' P. Z. S. 1894, p. 273. 



' Journ. Anat. vol. xiix. p. xii. 



