EAST AFRICAN MAMMALS IN NATIONAL MUSEUM. 



159 



is the prime factor in the delinitc mechanical action of separate parts 

 of the dental row. While the masseter, as stated above, has primarily 

 to do with the front teeth (the canines and incisors), the temporal 

 is chiefly concerned with the molar-premolar row, and the process of 

 cuttin<j; and chewing rather than biting and gripping. The lion, hke 

 all cats, is a biting animal of the highest type. The masseter, aided 

 by the temporal and internal pterygoid muscles, locks the jaw and 

 makes the grip firm. It is attached to ahnost the entire length of 

 the inner side of the zygoma, from just back of the molar tooth to the 

 pit on the upper side of the squamosal root, and to the ventral half of 

 the outer surface from near the maxillary tuberosity to near the 

 glenoid surface. The region of its origin in the McMillan skulls is 

 greatly changed from the wild type. The malar and the zygomatic 

 process of the temporal bone have 

 been almost uninfluenced by the 

 muscle and have to a certain de- 

 gree retained distinctive characters 

 of juvenility. In wild lions this 

 muscle has exercised very great 

 influence on the bones of the zygo- 

 matic arch. The following char- 

 acters, which appear to be largely 

 due to the nonaction of this 

 muscle, separate easily the Mc- 

 Millan lion skulls of either sex 

 from wild skulls of equal age: 

 Zygoma more spreading ante- 

 riorly; malar very thick and wide; 

 squamosal arm subterete and 

 heavy, almost rounded in cross 



section and not at aU concave on inner surface, with no superior 

 margin for strong muscle attachment [in skulls of wild-killed speci- 

 mens the squamosal arm of the zygoma is thin and hght, but 

 strong; it is greatly hollowed out on inner surface and has a sharp 

 superior margin]. The region of insertion, tlie outer lateral face 

 of the ascending mandibular ramus, is also greatly modified. In the 

 McMillan skulls it is comparatively heavy and thick, but is smooth 

 and poorly fitted for muscle attachment. The margin is smooth 

 and rounded. The great zygomatic breadth of the skull of the 

 captive lion is partly due to the rounded squamosal arm. 



Regions of attachment of the temiioral muscle. — The chief function of 

 the temporal muscles is to apply to the cheek teeth the power needed 

 for the crushmg and cutting up of the food killed by the canines and 

 incisors. As the lions in the Zoological Park are always fed with 

 pieces of meat containing large bones, in order to guard against the 



Figs. 2-3.— Cross sections of zygomata op wild- 

 killed AND PARK-KEAEED LION SKULLS, MADE 

 AT INFERIOR POINT OF ZYGOMATICO-TEMPOEAL 



SUTURE.— (2) Wild-killed (No. 155443, Nairobi. 

 British East Africa); (3) park-reared (No. 

 199707, "McMillan lion.") Adult males of 

 equal age. Nat. size. 



