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 " 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- 



