228 THE DOG-FISH. 



With the exception of the hindmost they bear 

 gill-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 gill-rays along their posterior borders. 

 The fifth or hindmost cerato-branohial is shorter 

 but much broader than the others ; it has no 

 gill-rays; and its posterior border is deeply 

 notched to lodge the Cuvierian sinus (p. 242). 



d. The hypo-branchials are small rods in connection 



with the inner ends of the first, second, third, 

 and fourth cerato-branchials. The first hypo- 

 branchial, which is very small, is directed for- 

 wards, and connects the first cerato-branchial 

 with the basi-hyal. The three hinder hypo- 

 branchials are larger, and are directed backwards. 



6. The basi-brancMal 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. (Fig. 

 49, p. 238.) 



f. The extra-branchials are three pairs of elongated 

 curved rods Ijing along the outer sides of and 

 beneath the second, third, and fourth branchial 

 arches. 



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

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

 mouth. 



D. The Skeleton of the Fins. 



1. The median fins. 



The skeleton of the dorsal fins consists of a series 

 of parallel rods of cartilage, the basal cartilages, 

 sloping upwards and backwards, and calcified along 

 their axes. The lower or basal ends of the rods 



