Fishes of the Western North Atlantic 235 



Genus Triakis Miiller and Henle, 1838 



Triakts Miiller and Henle, Charlesworth's Mag. Nat. Hist., 2, 1838: 36; Arch. Naturg., Jahrg. 4, t, 1838: 84 

 (no species mentioned) ; Plagiost., 1841: 63 ; type species, T. scyllium Miiller and Henle. Japan. 



Generic Synonyms: 



Triads Giinther, Cat. Fish. Brit. Mus., 8, 1870: 384; emended spelling for Triakis Miiller and Henle, 1838. 



Rhinotriacis G'lW, Proc. Acad. nat. Sci. Philad., 1862: 486; type species, R. henlei Gill. California. 



Calliscyllium Tanaka, Fish. Japan, 10, 1912: 17; type species, C. venusta Tanaka. Japan. 



Hemitriakis Herre, Philipp. J. Sci., 23, 1923: 70; type species, H. leucoferiftera Herre. Philippines. 



Generic Characters. Nostrils entirely distinct from mouth, their anterior margins 

 without barbel} teeth compressed, with 2, 3 or 4 pointed cusps, the axial longest; a labial 

 furrow on each jaw at corner of mouth; spiracles moderately large, easily seen. Characters 

 otherwise those of the family. 



Range. Until recently the genus was known only from the Indian Ocean (including 

 the Red and Arabian Seas), Malaysia, Melanesia and Polynesia, the western North Pa- 

 cific, and the eastern Pacific, north and south. Within the last few years it has been en- 

 countered in Cuban waters (p. 240). 



Species. The members of this genus show a wide gradation in the number of dental 

 cusps and in. the relative length and acuteness of the median member;' the dermal den- 

 ticles, too, may be either simple-lanceolate, partly or weakly tri dentate, or strongly so;* 

 and the labial furrows are very prominent in some but very short and inconspicuous in 

 others.' The several species also differ in the relative positions of the dorsal and anal fins, 

 the size and shape of the caudal, and in the proximity of nostril to mouth, these being the 

 characters employed in the accompanying Key because they are the most conspicuous. 



Key to Species 



I a. Origin of 2nd dorsal about over origin of anal or behind it, its tip over or posterior to 

 tip of latter; labial furrows very short. 



2a. Anterior margin of nostril close to mouth; rear tip of ist dorsal a little anterior 

 to origin of pelvics; tips of pelvics anterior to origin of 2nd dorsal by a distance 

 considerably longer than base of 2nd dorsal. venusta Tanaka, 1 9 1 2. 



Japan. 



2b. Anterior margin of nostril far from mouth; rear tip of ist dorsal posterior to 

 origin of pelvics; tips of pelvics anterior to origin of 2nd dorsal by a distance only 

 about y-i as long as base of 2nd dorsal. 



barbouri Bigelow and Schroeder, 1943, p. 236. 



7. Median cusp long and slender in scyllia, semifasciata and barbouri; only moderately so in venusta; short and 

 blunter in maculata and henlei. 



8. Denticles simple-lanceolate in scyllia, semifasciata and /tenlei; weakly tridentate in venusta; partly so in maculata; 

 strongly tridentate in barbouri. 



9. Labial furrows long and conspicuous in scyllia, semifasciata, henlei and maculata; very short in barbouri and 

 venusta. 



