516 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 



SYIVOPI§IS AND DKSCBfiPTlON.^i OE THE AITIIBRICAIV RUEIVOBATID^. 



By SAMUEL CJARITIAN. 



RHIXOBATID^. 



Trunk broad, flat ; tail long, strong, continuons with the body ; dor- 

 sals and caudal well developed ; pectorals not reaching the end of the 

 snout (except species of BiscohaUdae) ; covered with shagreen; with 

 spines in a vertebral row and on the shoulders ; generally viviparous. 



Rhinobatus. 



Nasal valves not extended upon the space between the nostrils ; 

 two flolds on the spiracle; rostral cartilage 

 medium, the ridges 

 separate ; 



snout pointed - leucorhynclius 



confluent half their length ; 



snout rounded on the end productus 



produced, narrow ; groove short, small ; ridges 



confluent more than half their length . spinosus 



long ; ridges straight, confluent 

 less than half their length ; 

 four patches of spines on the shoulders ; 



color uniform liorJcelii 



more than half their length ; 

 two patches of spines on shoulders ; 



clouded or blotched undulatus 



close together, narrowly separated at the base ; 

 rarely with spines on the shoulders ; 



freckled with whitish lentiginosus 



one fold on the spiracle ; snout blunt, rounded ; 

 head flat planiceps 



Syerhina. 



Nasal valves extended on the internarial space; 

 a fold on the hinder margin of the spiracle; 



rostral ridges meeting hrevirostris 



no fold on the spiracle; 



rostral ridges not meeting , exasperata 



Platyrhinoidis. 

 Labial fold distinct ; 

 no fold on the spiracle; 

 posterior lobe of nasal valve rudimentary , triseriata 



