432 



contains the brain and shelters the ears-and the jaws and gill-skeleton. The 

 shape and the position of the various bones entering into the cranmm may be 

 seen from fig % A. and B. In many fishes the cranium is largely cartilaginous, 



m- 



pm 

 pa. 



Fig. 3 A. CRANIUM AND ANTERIOR VERTEBRA 

 OP CATFISH FROM ABOVE. 



M, mesethmoid ; pm, prenaaxilla ; a, antorbital ; 

 n, nasal ; e, parethmoid ; fr, frontal ; s, apheno- 

 tic ; p, pterotic ; ep, epiotic ; t, supraclavicie ; so, 

 supraoccipital spine ; 4, transverse process of fourth 

 vertebra. 



Fig. 3 B. CRANIUM AND ANTERIOR VEKTEBR.E 



OF CATFISH, FROM BELOW. 



Pm, premaxila ; m, mesethmoid ; v, vomer ; pa> 

 parethmoid ; o, orbitosphenoid ; f, frontal ; ps> 

 parasphenoid ; a, alisphenoid ; pr, prootic ; h, arti- 

 cular surface for hyomandibular on sphen> and 

 pterotics ; b, basioccipital with exoccipitals on 

 either side ; s, supraclavicie; m, "maUeus;" 4, 

 5 and 6, transverse process of 4th, 5th and 6th 

 vertebrae. 



gristle or cartilage being only partly replaced by bones. In the Catfish, however, 

 there is little of this left in the adult fish. Attention is called to the position of the 

 vomer the teeth OD which sometimes furnish easily accessible characters to the syste- 

 matic zoologist. It is applied to the under surface of bones formed in cartilage, the 

 foremost of which, the middle ethmoid, carries in front the premaxillse, tooth - 

 bearing plates which form a considerable part of the margin of the upper jaw on 

 each side and which can in some fish be thrust out from their* support or 

 " protracted." The rest of the margin of the gape above is usually formed of the 



