RAYS. 337 



Pristis. — Body depressed and elongate, gradually passing into 

 the strong and muscular tail. Pectoral fins, with the front 

 margins quite free, not extending to the head. No tentacles 

 below the saw. Teeth in the jaws minute, obtuse. Dorsal fins 

 without spine, the first opposite or close to the base of the 

 ventrals. 



" Saw-fishes." Abundant in tropical, less so in sub-tropi- 

 cal seas. They attain to a considerable size, specimens with 

 a saw 6 feet long and 1 foot broad at the base not being of 

 uncommon occurrence. The saw, w^liich is their weapon of 

 attack, renders them most dangerous to almost all the other 

 large inhabitants of the ocean. Its endo-skeleton consists 

 of three, sometimes five, rarely four, hollow cylindrical tubes, 

 placed side by side, tapering towards the end, and incrusted 

 with an osseous deposit. These tubes are the rostral processes 

 of the cranial cartilage, and exist in all Eays, though in them 

 they are shorter and much less developed. The teeth of the 

 saw are implanted in deep sockets of the hardened integu- 

 ment. The teeth proper, with which the jaws are armed, are 

 much too small for inflicting wounds or seizing other animals. 

 Saw-fishes use this weapon in tearing pieces of flesh off an 

 animal's body or ripping open its abdomen. The detached 

 fragments or protruding soft parts are then seized by them 

 and swallowed. Five distinct species of Saw-fishes are known. 



Saw\s of extinct species have been found in the London 

 clay of Sheppey and in the Bagshot sands. 



Second Family — PiHinobatid^. 



Tail strong and long, ■with ttvo well-developed dorsal fins, 

 and a longitudi7ial fold on each side ; caudal developed. Disk 

 not excessively dilated, the rayed portion of the pectoral fins 

 not being continued to the snout. 



Rhynchobatus. — Dorsal fins without spine, the first opposite 

 to the ventrals. Caudal fin with the lower lobe well developed. 



Z 



