392 PROCEEDINGS OF THE ACADEMY OF [1880. 



are continuous anteriorly. It is probable that while the deep part 

 is absent from the temporal fossa proper, it remains in position in 

 the orbital space at a point answering to the post-septal depression 

 in animals having a partition between the orbit and the temporal 

 fossa. But while the deep part is absent from the proper temporal 

 fossa, a stout glistening tendon is here in the usual position of the 

 central tendon, and, as in Erethizon^ is concealed from without- 

 It is interesting to note that the supra-zygomatic slip is temporal? 

 it being doubtful whether any of its fibres are continuous with the 

 masseter. 



The masseter bears a general arrangement to the muscle in 

 Erethizon. The anterior edge is less muscular than in the latter 

 genus. The mandibulo-zygomatic portion, whose origin from the 

 mandibular angle occupies the lower one-third of the surface, con- 

 stitutes the massive fleshy belly. The fibres are for the most part 

 nearly horizontal. It is covered for the upper half of its surface by 

 the enormous malar bone. The slip from the median surface of the 

 mandible is arranged as in Erethizon. It lies in part in front, and 

 in part beneath the internal pterygoid. Its junction with the main 

 body of the masseter conceals the tendinous anterior edge thereof 

 and is continuous with those fibres arising from the angle and the 

 basal third of median surface. The deep mandibulo-maxillary 

 portion is as in Erethizon in all essential features. It is continu- 

 ous with the superficial parts. A thin layer of orbital fibres 

 OA^erlies the temporal muscle in the orbit. Another layer is 

 apparently continuous with the buccinator. 



In Dasyprocta the general plan of arrangement seen in Coelo- 

 genys is followed. The minute points of distinction therefrom not 

 being noteworthy save the continuance of the main tendon within 

 the orbital space, where it overlies the deep anterior vertical 

 fibres. 



In Cuvier and Laurillard (PI. 245) the slips of the temporal 

 are represented as parts of a bi-peniform muscle. I find the supra- 

 zygomatic fibres more horizontal in position, darker in color and 

 more convex than the remainder of the muscle. 



In the bats the superficial portion of the temporal may be small 

 or well developed. In the first variety a good example is seen in 

 Fhyllostoma hastatum and other American leaf-nosed bats in which 

 forms the superficial portion is confined to the anterior fourth 

 of the temporal fossa. The supra-zygomatic slip is also very 



