304 Memoir Sears Foundation for Marine Research 



Generic Characters. Carcharhinidae with anal less than twice as long at base as 2nd 

 dorsal; without spiracles; c?.udal peduncle without lateral ridges, but with a precaudal 

 pit below as well as above; midpoint of base of ist dorsal as near to axil of pectoral as to 

 origin of pelvics, or nearer; and dorsal only about ^o as long at base as ist and much 

 smaller in area; teeth slender and symmetrical in both jaws, their bases as well as their 

 cusps with smooth edges; gill openings notably large, the longest nearly or quite V2 as 

 long as base of ist dorsal and more than twice as long as horizontal diameter of eye (see 

 footnote 5, p. 265), the 5th being over origin of pectoral; anterior margin of nostril 

 only slightly expanded; labial furrow around corner of mouth but extending inward for 

 only a very <5hort distance onto either jaw, if at all. Characters otherwise those of the 

 family. 



Range. Tropical and subtropical. Senegambia in the eastern Atlantic; North Carolina 

 (perhaps New York) soutn to Cuba and Texas in the western Atlantic; tropical Indian 

 Ocean; Red Sea and Arabian Gulf; India; East Indies and Australia, Indo-China, Japan, 

 Micronesia. 



Species. This genus of small sharks, about which little is known, is represented by one 

 species in the Atlantic and by one in the Indo-Pacific.* 



Key to Species* 



la. Snout in front of mouth only about % (about 29%) as long as head, or % as long as 

 from eye to ist gill opening; distance between nostrils a little more than % as long as 

 snout; pectoral about V2 as long as head. isodon Muller and Henle, 1841, p. 304. 



lb. Snout in front of mouth about % (40%) as long as head, and about as long as from 

 eye to ist gill opening; distance between nostrils ^ as long as snout; pectoral about % 

 as long as head. brevifinna Muller and Henle, 1 841 . 



Arabia, East Indies, Australia, Japan. 



Afrionodon isodon (Muller and Henle), 1841 

 Figure 5 1 



Study Material. Two females, 460 and 504 mm., from off Biloxi, Mississippi, and 

 from Texas (U.S. Nat. Mus.) ; 4 young males, 500 to 567 mm., from Texas (Harv. Mus. 

 Comp. Zool.).* 



Distinctive Characters. Easily recognizable among local Carcharhinidae by its slender, 

 symmetrical, smooth-edged teeth, very long gill openings and a 2nd dorsal fin that is much 

 smaller than its ist dorsal. 



2. Another Indo-Pacific species, Carcharias acutidens Riippell, 1835, has usually been referred to this genus, but is 

 placed in Negaprion (p. 309) according to generic definitions adopted here. 



3. Carcharias jronlo Jordan and Gilbert (Proc. U.S. nat. Mus., 5, 1882: 102) is also referred to this genus by Beebe 

 and Tee-Van (Zoologica, N. Y., 28, 1941: 105), but it is placed here in Negafrion because of the large size 

 of its second dorsal fin; for discussion, see footnote i, p. 300. 



4. Contributed by J. L. Baughman. 



