184 FISHES OF MASSACHUSETTS. 



C. obscurus. Le Sueur. The dusky Shark. 

 Journal Academy Nat. Sciences, vol. i. p. 223, et fig. 



In a paper by Le Sueur upon " Several new species of 

 North American Fishes," in the first volume of the " Journal of 

 the Academy of Natural Sciences," a fish is described under 

 the name of " Squalus obscurus" which I have little doubt he 

 found in the waters of our state. Be that as it may, although 

 he does not mention its locality, he furnishes us with a good 

 figure of the species, and also of the upper and lower teeth. 

 The only two species of shark with which this could be con- 

 founded upon our coast, even by a careless observer, are the 

 " Carcharias vulpes" — Fox Shark, and u Lamna punctata" — 

 Mackerel Shark ; in both these species, the edges of the teeth 

 are smooth. In the " obscurus" however, they are deeply ser- 

 rated. In the winter of 1837, my brother-in-law, Thomas 

 M. Brewer, M. D., brought me a triangular serrate tooth, he 

 took from the jaw of a shark which had been cast ashore 

 at Nahant ; and in the summer of 1838, my friend Samuel 

 Cabot, jr., sent me a dozen teeth which he procured from 

 another shark at Nahant, evidently of the same species with 

 the preceding. Inasmuch then, as these teeth are triangular 

 and serrated, and the description of the specimens seen by these 

 gentlemen, answers to the plate of Le Sueur, I feel authorized 

 in admitting this species here. The following is Le Sueur's 

 description : 



" Tail with a carina undulated above, and slightly emarginat- 

 ed at the base ; pectorals long, narrow, and falciform ; dorsals and 

 anals projecting backwards in a point ; second dorsal opposite 

 to the anal, the latter bilobed. A white spot on each side of 

 the neck. Head flat and broad ; snout sharp edged, rounded 

 and wide at the end ; eyes lateral, large, orbicular, pupil trans- 

 verse ; narrow, with a nictitant membrane originating below ; 

 branchial apertures five, unequal, the first very large, the last 

 very small, and situate above the origin of the pectoral fins ; 

 nostrils oblique and partially covered by a short, pointed ap- 



