30 PISH GALLERY. 



side of those in use, in Cocliliodus the teeth are coalesced into a 



continuous plate, which receives additions to its lingual border 



and slowly moves outward and forward in a spiral manner over 



the surface of the jaw. Two views are given of the dental scroll 



of Cocliliodus, 25 and 26 (see also fig. 16). 



In the family Scylliidae the dorsal fins have no spines ; the 



first is situated above or behind the pelvic fins, The spiracle is 



distinct; there is no nictitating membrane. The teeth are small 



and several series are in use at the same 



time. The nasal and buccal cavities are 



more or less confluent ; the fourth and fifth 



gill-slits are close together in the genera 



Chiloscy Ilium, Crossorhinus, Ginglymos- 



toma, and Stegostoma, but not in Scyllium. 



Dog- The common Dog-fish of the South coast 



tisnes. Q f Ensland is Scyllium canicula, 30. The ' ' „ _, 7J . , 



° „,,. T-ii plates of Cocliliodus 



term " Dog-fish •' is applied loosely to any c ontortus. 



small Shark-like fish, the difference between (From Giinther, "Study 

 a Dog-fish and a Shark being one of size of Fishes.") 



only*. The Dog-fishes found around 



the British coast include the one just mentioned, Scyllium 

 canicula, 30, the Smaller Spotted Dog-fish ; the Larger Spotted 

 Dog-fish or Nurse Hound, Scyllium catulus, 27 ; and the following 

 three which do not belong to the family at present under considera- 

 tion, the Piked Dog-fish, Acanthias vulgaris (75, in Wall-case 2), a 

 Dog-fish which on the East coast is more common than the Spotted 

 Dog-fish ; the Smooth Hound, Mustelus vulgaris (68, Wall -case 2), 

 and the Tope, Galeus canis (6-4, Wall-case 2). The commonest of 

 these are the Smaller Spotted Dog-fish and the Piked Dog-fish, 

 which in some parts of the coast are sufficiently plentiful to prove 

 troublesome to fishermen by taking the bait intended for more 

 valuable fish. 

 Spotted The Spotted Dog-fishes are ground feeders and live mostly 

 tog-fish, on crustaceans and molluscs, and they keep fairly close to the land. 

 On some parts of the coast these Dog-fishes are eaten, but the flesh 

 is not in great favour. The smaller Dog-fish is distinguished from 



* This does not apply to extinct forms. Acanthodian fishes, for instance, 

 rarely exceed a foot in length, hut it is customary to speak of them as 

 " Sharks." 



