20 SELACHII: RALZ.— V. 
expanded pectoral fins. The tail is comparatively slender, and its 
fins are small. Spiracles present. The Aajide produce large eggs, 
enclosed in leathery cases; most of the other Raie are ovovi- 
viparous, bringing forth their young alive. 
Families of Raiz. 
a. Tail comparatively thick, with two dorsal fins; no serrated caudal spine 
nor cephalic fins. 
6. 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. . . - . PRistipipaA, 13. 
6b. Snout not saw- -like; disk ending abuapely at base of tail. 
c. Electric organs wanting; skin not perfectly smooth. . Raga, 14. 
ce. Electric organs present; a structure of honeycomb-like tubes between 
pectoral fins and head; skin perfectly smooth. . TorPEpINID&, 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&, 15. 
dd. Pectoral fins divided, leaving detached appendages (‘‘ cephalic fins ’’) 
on the snout. 
e. Teeth very large, flat, tessellated. . . . . . . AETOBATIDS, 16. 
ee. Teeth very small, flat or tubercular; size enormous, largest of the rays. 
MANTID&, 17. 
Famity XIII. PRISTIDIDAS. (Tue Saw-risuHEs.) 
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. (mpiorns, one who saws; the ancient 
name. ) 
24. P. pectinatus Latham. SaAw-risu. Saw with 25 to 28 
pairs of spines. L.10 feet. West Indies; occasional N. (Lat., 
comb-toothed. ) 
Famity XIV. RAJIDA. (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 
doreal 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 homis 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. . . . .. . Raga, 20. 
