298 BULLETIN 10 0, UNITED STATES NATIONAL MUSEUM 



small. Conspicuous dermal fold along each side of tail. Rayed 

 parts of pectorals not reaching snout, continued opposite gill 

 openings. 



Sharklike rays of warm seas, typically with an elongated body. 

 Ovoviviparous. Fossils known from the Cretaceous and later deposits. 



ANALYSIS OF GENERA 



a\ Ehininae. First dorsal origin above, before or immediately behind ven- 

 trals, which placed well behind pectorals ; subcaudal well developed ; pec- 

 toral not extending forward beyond level of mouth. 

 6\ Snout broad, rounded ; mouth deeply undulated ; nostril length less than 



internarial width; no spiracular folds Ehina 



h'. Snout elongate, narrow, pointed; mouth not deeply undulated; nostril 

 length greater than internarial width ; 2 spiracular folds- Rhynchobatus 

 a*. Rhinobatinae. First dorsal origin well behind ventrals; no distinct sub- 

 caudal; pectorals extend forward beyond level of mouth, well separated 

 anteriorly. 

 c\ Front nasal valves not united to form quadrangular flap. 



d^. Nostrils oblique or occasionally nearly transverse; inward extension 

 of front nasal valve ends on or crossing front margin of nostril ; 1 or 



2 spiracular folds Rhinobatos 



dJ'. Nostrils nearly transverse ; inward extension of front nasal valve 



crosses inner angle of nostrils Aptychotrema 



c'. Front nasal valve united to form quadrangular flap ; snout short, obtusely 

 pointed Trygonorrhina 



Genus RHINA Schneider 



Rhina Schneidee, Syst. Ichth. Bloch, p. 352, 1801. (Type, Rhina ancylostomus 

 Schneider, designated by Jordan and Evermann, Genera of Fishes, pt. 1, 

 p. 59, 1917. Rhina Schaffer 1760, Walbaum 1792, inadmissible, therefore 

 not preoccupying Rhina Schneider.) 



Demiurga Gistel, Naturg. Thierreichs, p. x, 1848. (Type, Rhina ancylos- 

 tomus Schneider, virtually. Demiurga Gistel proposed to replace Rhinu 

 Schneider. ) 



Rhamphoiatis Giix, Ann. Lyceum Nat. Hist. New York, vol. 7, p. 408, 1862. 

 (Type, Rhina ancylostomus Schneider, virtually. Rhamphoiatis Gill pro- 

 posed to replace Rhina Schneider.) 



Body depressed. Tail depressed, nearly half total length, slender, 

 continuous with body and pectorals. Body and head, also pectorals, 

 united as subtriangular disk, about one-third total length. Snout 

 broad, blunt, rounded. Mouth arched forward, deeply undulated. 

 Teeth larger on prominences. Nostrils nearly transverse, length of 

 each less than internarial width. Spiracles large, without folds. 

 Scales small, tubercles large and compressed. First dorsal above 

 ventrals. Caudal axis raised in fins, subcaudal lobed. Ventrals re- 

 mote from pectorals. 



Indo-Pacific. 



