COMPOSITION OF THE SKULL OF THE FISH. 87 



skeletons of animals. The compreliension of the descrip- 

 tion will be facilitated by reference to Figs. 7 and 9 ; and 

 still more if the reader have at hand the skull of any 

 large fish. 



In the cod {Gadns moirhuay, e.g.^ it may be observed, 

 in the first place, that most of the bones are, more or less, 

 like large scales ; have what, in anatomy, is called the 

 " squamous" character and mode of union, being flattened, 

 thinned off at the edge, and overlapping one another ; and 

 one sees that, though the skull, as a whole, has less free- 

 dom of m5vement on the trunk, more of the component 

 bones enjoy independent movements. Before we proceed 

 to pull apart the bones, it may be well to remark that the 

 principal cavities, formed by their coadaptation, are the 

 " cranium," lodging the brain and the organs of hearing ; 

 the " orbital," Fig. 9, or, and the "nasal," 7il, chambers ; the 

 buccal and branchial canals, hr. Some of these cavities 

 are not well defined. The exterior of the skull is tra- 

 versed by five longitudinal crests, intercepting four chan- 

 nels which lodge the beginnings of the great muscles of 

 the upper half of the trunk. The median crest is de- 

 veloped to an extreme height in some fishes, as, e. g., the 

 dolphin and light-horseman fish [Epkii^tpus). The flat- 

 fishes (turbot, sole, &c.) are remarkable for the unsym- 

 metrical character of the skull, in consequence of both 

 eyes being placed on one side of the head. 



In the analysis of the cod's skull it is best to begin at 

 the back part ; for the segm.ents of the skeleton deviate 

 most from the archetype as they recede in position to- 

 wards the two extremes of the body. After a little prac- 

 tice, one succeeds in detaching the bones which form the 



' The skull of this fish, conveniently prepared for this examination, 

 may be had of Mr. Flower, No. 22 Lambeth Terrace, Lambeth Road. 



4 



