DOG-FISHES. 31 



the larger, not only by its smaller size, but by its anal fin being 

 situated farther forward as compared with the second dorsal fin, 

 and the right and left nasal flaps are nearly continuous in front of 

 the mouth, whereas in Scyllium catulus they are some distance 

 apart. These Dog-fishes lay pillow-shaped eggs with a flexible 

 yellow-brown or black egg-shell, the four corners of which are 

 produced into tendril-like threads which serve to anchor the egg to 

 sea-weed and rocks (see specimen 4 in the introductory series 

 below the label "Elasniobranchii"). Two eggs are laid at a 

 time, and five or six months elapse before the embryo fish hatches 

 out. 



The Black-mouthed Dog-fish^ Pristiurus melanostomus, 31, is a 

 small Dog-fish common in the Mediterranean and occasionally 

 caught in British seas ; it has a series of small flat spines on each 

 side of the upper edge of the tail fin. The genus Ginglymostoma 

 includes Sharks some of which grow to twelve feet in length, with 

 small eyes and minute spiracles ; they are of pelagic habit and 

 occur in the warmer parts of the Atlantic and Indian Oceans. 

 The specimen of Ginglymostoma brevicaudatum shown (33) is 

 small, the jaws of the same species (34) give an idea of the size to 

 which the fish grows. A specimen of Ginglymostoma cirrhatum 

 (36) is shown on the floor of the case, and another specimen hangs 

 from the rail opposite Wall-case 2. 



In Chiloscyllium (e. g. Chiloscyllium indicum, 35) the anal fin 

 is far behind the second dorsal, and is almost continuous with the 

 caudal fin ; the genus includes several species of small Dog-fishes 

 occurring in the Indian Ocean and adjacent seas. Stegostoma 

 resembles Chiloscyllium in the backward situation of the anal fin, 

 but the spiracle is behind the eye instead of below it ; the eye is 

 very small, the snout very blunt, and the upper lip thick. The 

 Zebra Shark, Stegostoma tigrinum, is one of the commonest Zebra 

 Sharks of the Indian Ocean. In the young (e. g. 38) the tail fin Shark. 

 is proportionately much larger than in the adult (37), and the 

 colour- markings are more pronounced. This last feature is not 

 uncommon in Elasmobranch fishes, the young of many Dog-fishes, 

 Sharks, and Hays being brightly banded or spotted, whereas the 

 adults are of a uniform and dull coloration. Crossorliinus (39) 

 has a broad, fiat head with blunt snout and lateral projections of 

 skin ; the mouth is wide and nearly terminal ; the eye is small and 



