306 BULLETIN 10 0, UNITED STATES NATIONAL MUSEUM 



c". Snout short ; mouth width 214 to 3 iu preoral length ; space between 



spiracles 2% to nearly 3 in snout ; first dorsal base less than 3 times 



in interdorsal. 



f. Mouth width 2% to 2i^ in snout ; both spiracular folds well 



developed. 



g\ Space between rostral ridges rather narrow ; series of spines in 



median line of back; first dorsal base 214 to 2% in interdorsal. 



annandalei 



fir'. Space between rostral ridges broader ; series of minute tubercles 



in median line of back ; first dorsal base 2% in interdorsal. 



lionotus 

 f. Mouth width 2% to 3 in snout ; inner spiracular fold small or 

 rudimentary ; rostral ridges rather broad, narrowly separated 

 anteriorly ; median line of tubercles on back rudimentary. 



hynnicephalus 

 &l Front nasal valves extend inward well beyond level of inner nostril edge, 

 nearly meets that of opposite side. 



h^. Both spiracular folds developed ; mouth width 2V^ to ZV2 in 

 preoral length. 

 f\ Nostril length about equals internarial ; space between 

 spiracles 2 to 2% in snout. 

 y\ Mouth width 2% to 3 in preoral length; horizontal dis- 

 tance from' outer edge of nostril to lateral snout edge 3 

 to 3% in preoral length ; back with dark annular ocelli. 



annulatus 



f. Mouth width 2^/2 to 2% in preoral length ; horizontal 



distance from outer edge of nostril to lateral snout edge 



2V2 to 2% in preoral length ; snout and pectoral fins 



with pale bluish gray spots and blotches leucospilus 



i\ Nostril length 1% times internarial ; space between spiracles 

 nearly 3 times in snout. 



k^. Mouth width 3 in preoral length, 7^2 in space from 

 snout tip to front edge of vent ; horizontal distance 

 from outer nostril edge to lateral snout edge more 

 than four in preoral length ; coloration uniform. 



zanzibarensis 



k\ Mouth width SV2 in preoral length, more than 8 in 



space from snout tip to front edge of vent ; horizontal 



distance from outer nostril edge to lateral snout edge 



3% in preoral length ; back with numerous bluish gray 



ocelli ocellatus 



Ji^. Only outer spiracular fold developed; mouth width 2^4 to 2% 



in preoral length blochii 



a\ Rhinobatos. Front nasal valve extends inward on internarial space. 



r. Nostril length nearly 2 or 3 in mouth width, about 

 equals internarial. 

 m\ Snout very long, narrow, nostril ridges approxi- 

 mated for greater part their length ; mouth width 



2% to SVi in snout granulatus 



m'. Snout short, broad, rostral ridges more or less 

 separated throughout their length ; mouth width 

 1% in snout obtusus 



