ANATOMY OF VERTEBRATES. 



101 



arrangement which provides such an arch for each primary divi- 

 sion of the brain ; and a sentiment of admiration naturally arises 

 on examining the firm interlocking of the extended sutural sur- 

 faces, and especially of those uniting the proper elements of the 

 arch with the buttresses wedged in between the piers and key- 

 stone, and to which buttresses (diapophyses) the larger hrcmal 

 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,' fig. 

 81, 16, already mentioned; an ossified part of the eye-capsule, 

 commonly in two pieces, { sclerotals,' ib. 17 ; and an ossified part 

 of the capsule of the organ of smell, 'turbinal,' ib. 19. Another 

 assemblage of splanchnoskeletal bones support the gills, and are 

 in the form of slender bony hoops, called 'branchial arches,' 

 fig. 85, 48, 49. They are partly supported by the hyoidean arch. 

 Amongst the bones of the muco-dermal system, may be noticed 

 those that circumscribe the lower part of the orbit, fig. 75, g, g\ 

 of which the anterior, ib. 73, is pretty constant in the vertebrate 

 series, and is called ' lacrymal.' In fishes they are called ' subor- 

 bitals,' and are occasionally prssent in great numbers, as, e. g., in 

 the Tunny, or developed to enormous size as in the Gurnard, 

 fig. 82, and allied fishes, thence called ' mail-cheeked.' A similar 



82 



Fore part of the skeleton of the Gurnard (Tri/jla Lyra) 



series of bones called ' supertemporals ' sometimes overarches the 

 temporal fossa. 



At the outset of the study of Osteology it is essential to know 

 well the numerous bones in the head of a fish, and to fix in the 

 memory their arrangement and names. The latter, as we have 



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