210 THE DOG-FISH 



Skulls, like that of the dog-fish, in which the 

 hyoidean arch forms the suspensorium are spoken 

 of as hyostylic. 



3. The branchial arches are the remaining five visceral 



arches : they diminish in size from before backwards, 

 and each is divided into four segments on each side. 



a. The pharyngo-brancMals, the most dorsal elements, 



are slender rods running forwards and outwards 

 in the roof of the pharynx. The anterior ones are 

 connected with their fellows of the opposite side 

 by ligament ; and the last two of each side are 

 much smaller than the others, and fused together. 



b. The epi-branchials are short broad plates attached 



to the outer ends of the pharyngo-branchials. 

 With the exception of the hindmost they bear 

 giU-rays along their posterior borders. 



c. The cerato-branchials are stout rods running forwards 



and inwards in the ventral wall of the pharynx, 

 and bearing gUl-rays along their posterior borders. 

 The fifth or hindmost is shorter but much 

 broader than the others, and has no giU-rays. 



d. The hypo-branchials are small rods running back- 



wards and inwards from the inner ends of the 

 second, third, and fourth cerato-branchials. 



e. The basi-branchial is an elongated flattened median 



plate, pointed behind. It is connected with the 

 two hinder pairs of hypo-branchials in front, and 

 at the sides with the fifth cerato-branchials. With 

 these latter, it strengthens and supports the dorsal 

 wall of the pericardial cavity. 

 The extra-branchials are three pairs of elongated 

 curved rods placed along the sides of, and beneath 

 the second, third, and fourth branchial arches. 



4. The labial cartilages are two pairs of slender cartila- 

 ginous rods placed in the folds of skin at the sides of 

 the mouth ; and a couple of small cartilages near the 

 margin of the opening of each olfactory capsule. 



