20 SELACHII: RALE. — V. 



expanded pectoral fins. The tail is comparatively slender, and its 

 fins are small. Spiracles present. The Rajidce produce large eggs, 

 enclosed in Leathery cases; most of the other Raice are ovovi- 

 viparous, bringing forth their young alive. 



Families of Raiae. 



•. Tail comparatively thick, with two dorsal fins; no serrated caudal spine 

 nor cephalic tins. 

 b. Snout much produced, flat, armed with strong teeth on each side, set 

 at right angles to its axis; body somewhat shark-like, the disk grad- 

 ually passing into the tail Pristidid^e, 13. 



bb. Snout not saw-like; disk ending abruptly at base of tail, 

 c. Electric organs wanting; skin not perfectly smooth. . Rajid.e, 14. 

 cc. Electric organs present ; a structure of honeycomb-like tubes between 

 pectoral tins and head; skin perfectly smooth. . Tokpedinid.e, 14. 

 aa. Tail slender, with but one dorsal fin or none, and usually armed with a 

 serrate. 1 spine. 

 d. Fectoral fins uninterrupted, confluent about the snout; teeth small. 



DasyatidvE, 15. 

 r?c7. Pectoral fins divided, leaving detached appendages ("cephalic fins") 

 on the snout. 



e. Teeth very large, flat, tessellated Aetobatid.e, 16. 



ee. Teeth very small, flat or tubercular ; size enormous, largest of the rays. 



Mantidji, 17. 



Family XIII. PRISTIDID^E. (The Saw-fishes.) 



Rays with elongate body, stout, thick tail, and a long saw-like 

 snout, below which is the inferior mouth with small blunt teeth. 

 Dorsals and caudal well developed. One genus, with 5 or 6 species, 

 in warm seas. 



19. PRISTIS Latham. (Trpia-rqi, one who saws ; the ancient 



name.) 



24. P. pectinatus Latham. Saw-fish. Saw with 25 to 28 

 pairs of spines. L. 10 feet. West Indies; occasional N. (Lat., 

 comb-toothed.) 



Family XIV. RAJIDCE. (The Skates.) 



Rays with the disk broad, rhombic, more or less rough; the 

 males usually with about two rows of strong spines on each pec- 

 toral ; tail rather stout, with a fold of skin on each side, and two 

 dorsal fins above : caudal fin small or obsolete ; no serrated spine ; 

 no electric organs. Egg in a large leathery case, four-angled, and 

 having two tubular horns at each end. Genera 4, species 40, 

 mostly of the Northern seas. 



a. Caudal fin rudimentary; pectorals not confluent, leaving a translucent 

 area at the snout ; ventrals deeply notched Raja, 20. 



I 



