Table of Contents
The members of the genus Carcharhinus are set apart from other Atlantic members of the family Carcharhinidae by the following combination of characters: The mid-point of base of the first dorsal fin is at least as near to the level of the axils of the pectorals as to the level of the origin of the pelvics (separating them from the blue shark, p. 38); no labial furrows on lower jaw, and furrow on upper jaw reduced to a very short slit at the extreme corner of the mouth, directed outward (separating them from the tiger shark, p. 37, and from the sharp nosed shark, p. 40); second dorsal fin much smaller than first dorsal (separating them from the lemon shark, p. 35, footnote 85); edges of upper teeth more or less finely serrate but without larger denticles near the base, and edges of lower teeth perfectly smooth, without lateral denticles (separating them from the tiger shark, p. 37, from the sharp-nosed shark, p. 40), and from Paragaleus pectoralis, a tropical shark that has been taken off southern New England.
This is a warm-water group, fifteen species of which are known to inhabit the western side of the Atlantic, most of them resembling one another closely in general aspect. Only one of these (the dusky shark, described on p. 41) has yet been reported reliably from within the confines of the Gulf of Maine, while only one other (the brown shark, p. 43) is likely to be found there. If a stray Carcharhinus from offshore that does not agree with the following descriptions of one or other of these should be taken on Georges Bank, or on Nantucket Shoals east of the longitude of Cape Cod, we hope that its captor can identify it by means of the keys and descriptions of the genus that we have given in Part 1 of the Fishes of the Western North Atlantic.
 For description, see Bigelow and Schroeder, Fishes of the Western North Atlantic, Pt. 1, 1948, p. 276.