Fishes of the Western North Atlantic 325 



1 3b. First gill opening nearly twice as long as horizontal 

 diameter of eye, or longer} lower precaudal pit 

 strongly marked; fins conspicuously tipped with 

 black; anterior margin of nostril only slightly ex- 

 panded (Figs. 63 G, 67 B). 

 14a. Origin of ist dorsal about over midpoint of 

 inner margin of pectoral; ist gill opening less 

 than 2.5 times as long as horizontal diameter 

 of eye ; horizontal diameter about V5 as long 

 as snout in front of mouth; edges of lower 

 teeth regularly though very finely serrate. 

 Umbatus Muller and Henle, 1841, p. 346. 

 14b. Origin of ist dorsal over or a little posterior 

 to inner corner of pectoral; ist gill opening 

 more than 4 times as long as horizontal diam- 

 eter of eye; horizontal diameter of eye only 

 about Vt' to Vs as long as snout in front of 

 mouth; margins of lower teeth smooth. 



maculipinnis Poey, 1866, p. 364. 



Carcharhinus acronotus (Poey), 1861 



Black-nosed Shark 



Figure 55 



Study Material. Two males, about 485 mm. long, either embryo or newborn with 

 umbilical scar still showing, from Rio de Janeiro; 2 male embryos, 358 and 371 mm., 

 from Cuba; male embryo, 480 mm., about ready for birth, from Brazil (Harv. Mus. 

 Comp. Zool., No. 723); immature female, 637 mm., from Englewood, Florida (U.S. 

 Nat. Mus., No. 10433 ^ ) > also photographs of Poey's unpublished drawings of this species. 

 Distinctive Characters. Easily recognized, among those of the smooth-backed mem- 

 bers of the genus in which the second dorsal originates above the origin of the anal, by the 

 relatively long snout, combined with the fact that the upper teeth are noticeably asym- 

 metrical with deeply notched outer edges and much more coarsely serrate bases than tips. 

 Description. Proportional dimensions in per cent of total length. Male, 485 mm., 

 from Rio de Janeiro (Harv. Mus. Comp. Zool., No. 701). Female, 637 mm., from Engle- 

 wood, Florida (U.S. Nat. Mus., No. 10433 1). 



Trunk at origin of pectoral: breadth 10.7, li.O; height 1 1.5, i i.O. 



Snout length in front of: outer nostrils 3.7, 3.6; mouth 8.0, 8.0. 



Eye: horizontal diameter 2.5, 1.9. 



Mouth: breadth 7.2, 7.2; height 4.5, 4.2. 



Nostrils: distance between-inner ends 4.7, 4.7. 



