82 A Guide to the Zoological Collecliofis 



Family V. Scylliiclce [Case 38]. 



The Dog-fishes have no nictitating- membrane, and 

 their first dorsal fin is placed far back, above or behind 

 the ventral fins. They are usually of small size and are 

 not dangerous to man : they live chiefly on mollusks and 

 crustaceans. The genera found in India are Scyllium, 

 which occurs in all seas; Ginglymostoma, which also 

 occurs in the Atlantic and the Red Sea ; and Chiloscyllium 

 and Stegostoma, which are restricted to the Indian and 

 Western Pacific Oceans. Stegostoma is the " Tiger- 

 shark," a common Indian form, which grows to a length 

 of 10 or 15 feet. Ginglymostoma also grows to a large 

 size. 



Family VI. Spincwidce [Case 37]. 



The Spiny Dog-fishes of these seas are recognized by 

 the presence of a spine at the fore end of each dorsal fin. 

 Only two Indian species are known, namely, (1) Centro- 

 phorus Rossi from 430 fathoms, and (2) Centroscyllium 

 ornatum from 285 to 690 fathoms. Other species of 

 Centrophorus are found in the Atlantic and Mediter- 

 ranean, and of Centroscyllium near Arctic and Antarctic 

 seas. 



Batoidei (Rays). 

 All of the six known families of Rays are represented 

 in Indian Seas. 



Family I. Vvistidce [Cases 36-37J. 



The Saw-fishes resemble Sharks in form of body, but 

 the gill-openings are like those of the Rays in being on 

 the ventral surface. The snout is produced to form a 

 long narrow flat blade, which is armed with strong teeth 

 along both edges and is a formidable weapon of offence. 

 Saw-fishes grow to a length of 20 feet. Of the four 



