48 GENERAL AXD SPECIAL NAMES OF BONES. 



pleurapophysis and haemal spine, is sliort and thick; but 

 they send a long process backwards. This element is 

 called " maxillary," No. 21. The hasmal spine, cleft at 

 the middle line, sends one process upwards, of varying 

 length in different fishes, and a second downwards and 

 backwards ; and its under surface is beset with teeth in 

 most fishes ; it is called " premaxillary," No. 22. Each 

 pleurapophysis supports a " diverging appendage," con- 

 sisting commonly of two bones: the outer one, which fixes 

 the present haemal arch to the succeeding one, is called 

 "pterygoid," No. 2i; the inner one is the "entopterygoid," 

 No. 23. The entire segment is called the "nasal verte- 

 bra." The haemal arch and its appendage form what is 

 termed the upper jaw {maxilla)] the palatine and ptery- 

 goids forming the roof of the mouth, the maxillary and 

 premaxillary the proper upper jaw. On reviewing the 

 arrangement of the bones of the foregoing segments, one 

 cannot but be struck by the strength of the arches which 

 protect and encompass the brain, and by the beauty and 

 efficiency of that arrangement which provides such an 

 arch for each primary division of the brain ; and a senti- 

 ment of admiration naturally arises on examining the 

 firm interlocking of the extended sutural surfaces, and 

 especially of those uniting the proper elements of the 

 arch with the buttresses wedged in between tlie piers and 

 keystone, and to which buttresses (diapophyses) the 

 larger hremal arches are suspended. 



In addition to the parts of the neuroskeleton, the bones 

 of the head include the ossified part of the ear-capsule, 

 "petrosal," 16, already mentioned; an ossified part of the 

 eye-capsule, commonly in two pieces, " sclerotals. No. 17; 

 and an ossified part of the capsule of the organ of smell, 

 " turbinal," No. 19. Another assemblage of splanchno- 



