FISHES OF THE GULF OF MAINE 



41 



is about over the inner corners of the pectorals 

 when the latter are laid back; its height is about 

 one-half as great as the distance from the tip of 

 the snout to the level of the origin of the pectorals. 

 The second dorsal is only about one-quarter as 

 high as the first; its point of origin is about over 

 the mid-point of the base of the anal fin ; the anal 

 is a little larger than the second dorsal. The tail 

 fin occupies about one-quarter of the total length 

 of the shark; its lower lobe (measured along the 

 anterior edge) is a little less than one-half as long 

 as the upper lobe, the rear edge of which is deeply 

 notched near the tip. The pectoral fins are smaller 

 relatively than in any other local species of this 

 family, their length, armpit to tip, being only a 

 little greater than the height of the first dorsal 

 fin. The teeth are alike in shape in the two jaws, 

 sharp-pointed and smooth edged; those in the 

 center of the mouth are symmetrical and erect, 

 but those along the sides have weakly concave 

 inner margins, but deeply notched outer margins, 

 and are increasingly oblique toward the corners 

 of the mouth. 



Color. — Brown to olive gray above, with the dorsal 

 and caudal fins more or less dark edged; white 

 below and along the rear margins of the pectorals. 



Size. — Mature specimens are commonly between 

 26 and 30 inches long; a few grow to 36 inches. 



General range. — Both sides of the tropical-sub- 

 tropical Atlantic; Morocco to Cameroon and the 

 Cape Verde Islands in the east ; Uruguay to North 

 Carolina in the west; occasional to Woods Hole, 

 and as a stray to the Bay of Fundy. 



Occurrence in the Gulf of Maine. — Our only 

 reason for including this warm-water shark is 

 that one was taken at Grand Manan Island, 89 at 

 the mouth of the Bay of Fundy, in 1857. 1 "" 2 



Early reports of it from Newfoundland were 

 based on a misconception. 



Sharks of the Genus Carcharhinus 



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 



" This specimen, collected by A. E. Verrill, Is in the Museum of Com- 

 parative Zoology. 



1-1 See Jordan and Evermarm, Bull. 47, V. S. Nat. Mus., Pt. 1, 1896, p. 43, 

 footnote. 



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 pecloralis, a tropical shark that 

 has been taken off southern New England. 3 



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. 



Dusky shark Carcharhinus obscurus (LeSueur) 



1818. 



Bigelow and Schroeder, 1948, p. 382. 



Description. — The combination of characters 

 that place the dusky shark among the western 

 Atlantic members of its genus are: Trunk about 

 one-fifth as high at first dorsal fin as it is long to 

 origin of the caudal fin, tapering both forward 

 and rearward; snout broadly rounded in front, its 

 length in front of the nostrils less than the distance 

 between the nostrils; the front edge of the nostril 

 is not expanded as a definite lobe; the midline of 

 the back between the two dorsal fins has a low 

 but definite ridge, a character which is very pre- 

 cise, though seemingly minor; the first dorsal fin is 

 considerably smaller than in the brown shark 



' For description, see Bigelow and Schreeder, Fishes of the Western North 

 Atlantic, Pt. 1, 1948, p. 276. 



