FAMILY, IV— SCTLLIID^. 727 



Sub-Oeder, II— BATOIDEL 



Spiracles present : gill-openings in five pairs, and on the ventral surface of the body. Body depressed, 

 forming, due to largely-developed pectoral fins, a more or less flat disk, and having usually a thin and slender 

 tail. Dorsal fin, when present, in the caudal portion of the body : anal absent. 



Skates and rays exist in enormous numbers in the Indian seas, where they attain to a great size, and some 

 are dreaded by fishermen because of the -wounds inflicted by their caudal spines, while others cause great injury 

 to the oysters. Skates are gregarious, and may suddenly arrive to the dismay of the owner of an oyster bed, 

 as they appear to remain so long as any molluscs are to be obtained. Rays lie concealed in the sand, and 

 are reputed to be able to suddenly encircle fish or prey swimming above them with their long whip-like tails, 

 and then wound them with their serrated tail spine. Their skins were formerly valuable as shagreen, being 

 considered superior to those of sharks, owing to the scales being of somewhat larger dimensions. Irrespective 

 of being employed for shagreen, they are occasionally used as rasps or sand-paper, to give the first surface to 

 ■wood or horn which it is desired to polish. Their fins are exported along with those of the sharks to China, 

 ■where they are used for soups, while from their livers an oil is extracted. 



The thin horny eases, inside which are the fcetal rays, are more square in form and comparatively 

 smaller than what are observed among the sharks. Many of these cases are square, with a horn-like projection 

 from each corner. 



SYNOPSIS OF FAMILIES. 



I. PRiSTlDiE. A flattened snout, ha^wng lateral teeth, rendering it saw-like, p. 728. 



II. Rhinobatid*. Pectoral fins not continued to the snout. Trunk gradually passing into the tail, 

 which has two dorsals and a caudal fin, p. 730. 



III. T0RPEDINID.E. Trunk a broad smooth disk. Usually dorsal and caudal fins. An electric 

 organ, p. 733. 



IV. Rajidj). Trunk a broad and generally a rough disk. Pectoral fins extend on to the snout. A fold 

 along either side of the tail : no serrated caudal spine. No electric organ, p. 73.5. 



V. Tetgonid^. Pectoral fins extend on to and are confluent at the snout. No fold along side of tail : 

 which latter is usually armed with a sen-ated spine, p. 736. 



VI. Myliobatidj;. Pectoral fins do not extend on to the side of the head : snout with a detached 

 pair of fins, p. 742. 



