394 PROCEEDINGS OF THE ACADEMY OF [1880. 



is more concealed owing to the greater development of the anterior 

 fibres. Those in Noctilio appear to be directly continuous with 

 fibres arising from the occipital crest and inserted on the outer 

 surface of the main tendon. With respect to the masseter it may 

 be said to be simpler than the typical description given at the 

 beginning of this paper. It possesses but slight tendencj'^ to 

 planal cleavage. 



In the bovine type of the ruminants as seen in the head of a 

 calf the first or superficial layer of the temporal is continuous 

 with the masseter as shown In the above forms, the deep layer is 

 much less conspicuously developed than in them. The temporal 

 fossa being shallow — and not high — the central tendon is pro- 

 duced backward and is relatively small and insignificant. It is 

 not traceable over a short distance beyond the top of the coro- 

 noid. 



The masseter muscle possesses six layers. The first is broad 

 and attached to the superior maxilla by an oblique line extending 

 the entire distance from the inferior border of the orbit to the 

 gum line over the first molar. The second arises tendJnously from 

 the angle of the lower jaw and extends obliquely upward and for- 

 ward, halfway up the ascending ramus. The third layer is tendi- 

 nous at the anterior superficies of the malar bone, the fibres 

 arising thence including the anterior half of the surface of the 

 zygoma. The fourth la3'er arises from the inferior border of the 

 zygoma at its anterior two-thirds, and is inserted muscularly upon 

 the ramus about midway between the zygoma and the lower border 

 of the mandible. It is this layer which is continuous with the 

 temporal as in other quadrupeds. 



The masseter exhibits a fifth slip which appears to be a differ- 

 ential from the second or third layers, it overlies the temporo- 

 maxillaiy articulation in the form of a well-defined bundle which 

 arises tendinously from the root of the z3'goma. It is inserted 

 on the ramus near the posterior border at about its middle. A 

 sixth layer exists in the form of a narrow, bright tendon and asso- 

 ciated fibres arising from the I'oot of zygoma beneath the fore- 

 going. 



Nothing similar to the fifth and sixth layers were seen in the 

 other animals examined. The sixth layer of the dog being rather a 

 sub-division over the ramus in front of and remote from the joint. 

 It is every way likely, however, that the number of the layers in 



