102 



ELEMENTAR Y ANA TOMY. 



LESS. 



The frontals may develop great bony processes, which are 

 the bony cores supporting the corneous sheaths of hollow- 

 horned Ruminants, as e.g. in the Goats. They may also 

 periodically develop branched pro- 

 cesses, " antlers," as in Deer. 



These will be more conveniently 

 considered in the Seventh Lesson. 



22. The TEMPORAL bone of man 

 is the representative not only of a 

 number of distinct bones in lower 

 animals, but of bones of very differ- 

 ent natures both as to origin and 

 function. 



What answers to the squamous 

 portion in man, is called the " squa- 

 mosal" in lower animals. 



In man it is of greater relative 

 size, and takes a larger share in the 

 formation of the inner cranial wall 

 than is the case in most of his 

 class, though, strange to say, it 

 becomes again relatively larger in 

 one of the very lowest of Mammals, 

 i.e. the Echidna. 



Below the Mammalia it becomes 

 excluded from all share whatever 

 in bounding the cranial cavity, and 

 may be a mere bar contributing to 

 form the bony scaffolding of the 

 skull, as in Lizards or as in bony 

 Fishes. A portion of it may descend 

 from the cranium altogether, and 



FIG 99. Upper view of the 



;ull o" 

 centetas; showing the ab- become a mere part of ^ giU-cover 



Skull of the Tanrec, Hem 



sence of a zygomatic arch on 



each side. flap, the pre-operculum. 



The function of suspending the 



lower jaw is one peculiar to this element of the skull in 

 Mammals, while in all Vertebrates below Mammals the 

 squamosal has no part in such an office. 



Amongst his own class, man presents a medium develop- 

 ment of the glenoid surface, which may be much more con- 

 cave than in him (as in Carnivora), or much less so (as in 

 Ruminants). 



Its antero-posterior concavity is thus most marked in the 

 hard-gripping Badger, where the anterior and posterior bony 



