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 Eaice are ovovi- 

 viparous, bringing forth their young alive. 



Families of Raise. 



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



nor cephalic fins. 



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. . RAJIDCE, 14. 



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



pectoral fins and head ; skin perfectly smooth. . TOKPEDINID^E, 14. 



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



serrated spine. 

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



DASYATID^E, 15. 



dd. 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. 



MANTIDJK, 17. 



FAMILY XIII. PRISTIDIDJE. (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. (TrptVr?;?, 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. 



