THE SKULLS OF FISHES. 



195 



them are doubtless, as Miiller has suggested, the analogues of 

 labial cartilages. 



b. The cartilaginous cranium with a mandible and a fixed 

 suspensorium. 



The Hohcepliali, or Chimseroid fishes (Chimsera and Callo- 

 rliijnehus) present this type of cranial organization. In accord- 

 ance with the large development of the brain, the skull of these 

 fishes has attained a great advance in dimensions over the spinal 



Fig. 77. 



Fig. 77. — Skull of Callorhynchus Antarcticus (after Miiller). — a, anterior tooth of the 

 upper jaw ; c, posterior tooth ; b, mandibular tooth ; d, e, /, g, h, i, k, I, m, accessory 

 labial, nasal, and rostral cartilages ; n, quadrate portion of the sub-ocular plate which 

 supports the hyoid (o) and the mandible {Mn) ; p, the representatives of branchiostegal 

 rays ; q, the branchial arches ; Au, auditory region ; Or., orbit ; V 1 , nasal division of 

 the fifth nerve. 



column, and presents a large internal chamber. It is a con- 

 tinuous cartilaginous mass, without any superior aperture of suf- 

 ficient size to deserve the name of a fontanelle, in the base of 

 which the notochord does not persist, and which is definitely 

 articulated by two lateral convex facets and a median concave 

 surface on the hinder margin of its floor {A, Fig. 78) with the 

 anterior segment of the spinal column. 



The skull is high and compressed from side to side ; pos- 

 teriorly, it exhibits, on each side, an enlargement (Au), which 

 lodges the auditory organ. In front of these are the large 

 orbits (Or.), separated by a thin membranous inter-orbital septum 

 (LOr.), which is unlike the inter-orbital septum usually met with, 



o 2 



