Fishes of the Western North Atlantic 359 



are white tipped. In embryos, however, the dorsals, pectorals, pelvics and lower lobe of 

 caudal are more or less conspicuously tipped with sooty gray or black. 



Size. The stage of development of the embryos listed above (up to about 580 mm. 

 long) suggests a length of perhaps 650 to 700 mm. at birth. Maturity probably is not 

 reached at less than about six feet. The longest for which we find exact measurement was 

 3.5 meters (about 1 1 V2 feet). The maximum size is said to be 12 to 13 feet, but we think 

 it likely that at least some may grow considerably longer, for larger sharks, apparently of 

 this species because of the rounded shape of the first dorsal fins, have been described re- 

 cently to us as seen at the surface over the continental slope in the offing of Woods Hole 

 from the research vessel "Atlantis." 



Developmental Stages. Development is viviparous j the embryos which we have col- 

 lected" have a long umbilical cord, about 410 mm. in length, terminating in a well devel- 

 oped yolk-sac placenta by which they were attached to the uterine wall of the mother, 

 C. longimanus is also peculiar among carcharhinids for the very considerable changes in 

 the shape of its fins with growth, as illustrated by drawings of the embryo and mother 

 shown in Fig. 64, and emphasized above in the description. It is interesting that in one 

 case all members of a litter of embryos were of the same sex (female), whereas in another 

 case both sexes were represented (see Study Material, p. 354). 



Remarks. C. longimanus very commonly has been confused with leucas, which it re- 

 sembles in general form of trunk, very broad head, very short and broadly rounded snout, 

 low-arched mouth, relative positions of fins, and teeth; consequently the synonymy of the 

 two species is almost hopelessly confused. Actually, however, the two species are separable 

 at a glance by the shape of the first dorsal fin (strongly rounded in longimanus, but sub- 

 angular in leucas) ; also the tip of the anal reaches nearly to the precaudal pit in longimanus 

 but falls considerably short of it in leucas, and the pectoral is much longer, relatively, in 

 the former than in the latter. The outline of the lower lobe of the caudal is also distinctive, 

 being convex posteriorly and nearly straight anteriorly in adult longimanus with the re- 

 verse in leucas, while the margins of the dermal denticles are much more strongly toothed 

 in leucas than in longimanus. The differences in the shapes of the fins, especially the pec- 

 toral, are even more striking in the case of embryos than of adults. 



Habits. Astonishingly little is known of the habits of longimanus, considering that it 

 is one of the members of its genus that has been recognized the longest. Apparently it is 

 more strictly pelagic than any other members of Carcharhinus in the western Atlantic, and 

 more strictly tropical there than most of them are. We have not found a single report of 

 one caught from the beach or taken in a pound net anywhere along the coast of the United 

 States that can be referred with certainty to this particular species.'* And while "Carcharias 



57. See Study Material, p. 354. 



58. Jordan, it is true (Bull. U.S. nat. Mus., 7, 1884: 104), has characterized a large shark under the name Car- 

 charias lamia as very common around wharves and off the Keys of southern Florida, adding that one of 5 or 6 

 embryos which were taken from a yyi-ioot female was kept. But the subsequent illustration, probably of this 

 specimen (Jordan and Evermann, Bull. U.S. nat. Mus., 47 [4], 1900: pi. 5, fig. 17), is not of a longimanus but 

 apparently of a leucas. 



