NO. 2196. EFFECTS OP ENVIRONMENT ON LIONS— HO LUSTER. 



185 



temporal and internal pterygoid muscles, it locks the jaw and makes 

 the grip firm. The region of its origin in the McMillan skulls is 

 greatly changed from the wild type. The malar ;ind the zygomatic 

 process of the temporal bone ^ have been almost uninfluenced by the 

 muscle and have to a certain degree retained distinctive characters 

 of juvenility. In wild lions this muscle has exercised very great 

 influence on the bones of the zygomatic 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 all con- 

 cave on inner surface, with no 

 superior margin for strong mus- 

 cle attachment [in skulls of wild- 

 killed specimens the squamosal 

 arm of the zj'goma is thin and 

 light, but strong; it is greatly 

 hollowed out on inner surface 

 and has a sharp superior margin]. The region of insertion, the 

 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. 

 Some measurements of two old adult male skulls of equal age are 

 as follows : 



1 2 



Fios. 1-2.— Cross sections of ztgomata of wild- 

 killed AND PARK-REARED LION SKULLS, MADE 



at inferior point of zygomatico- temporal 

 suture.— (1) wild-killed (no. 155443, nairobi, 

 British East Africa); (2) park-reaeed (No. 

 199707, "McMillan lion.") ADin,T males of 



EQUAL AGE. NAT. SIZE. 



Condylobasal length 



Zygomatic breadth 



Greatest thirknes." of zygoma at middle 



Actual thickness of bone at middle of zygoma 



Thickness at inferior zygomatico-tomporal suture 



Ileight of arch at middle, across malar and zygomatic process of 

 temporal 



31.9 



36.9 



•The masseter is sittachod to almost the entire length of the inner side of the 

 nygonia, from just back of the molar tooth to the pit on the upper side of the squamosal 

 root, and to the vontral half of the outer surface from near the maxillary tuberosity 

 to near the glenoid surface. 



