244 



Memoir Sears Foundation for Marine Research 



Mustelus cams (Mitchill) ,1815 



Smooth Dogfish 



Figures 42 A-E, 43 C 



Study Material. Numerous specimens from southern New England and New York, 

 newborn to adult, living, fresh-caught, and preserved} also preserved specimens from 

 South Carolina j Galveston, Texas; Havana, Cuba; Jamaica; Trinidad (embryo); Ber- 

 muda; and Brazil, including three embryos from Rio de Janeiro. 



Distinctive Characters. M. canis is very closely allied to M. mustelus of the eastern 

 Atlantic, but is separable from the latter by the narrower pectoral fin, relatively greater 

 distance between the nostrils and the much more strongly sculptured denticles. Among 

 western Atlantic species of the genus it is distinguished from schmitti in that the lower 

 anterior corner of its caudal forms a lobe and that the distance between its nostrils is rela- 

 tively greater, that is, approximately half as great as the breadth of the mouth (only 

 about a third as great in schmitti) ; from norrisi in that its lower caudal lobe is rounded 

 rather than pointed and that the midpoint of its first dorsal is as close to the axil of the pec- 



FicuRE 42. Mustelus canis, male, 78 1 mm. long, from Woods Hole, Massachusetts (Harv. Mus. Comp. Zool., 

 No. 35245). A Head to pectorals. B Cross section of trunk, midway between the two dorsal fins, to show mid- 

 dorsal ridge. C Dentition of right-hand side of upper jaw, about 2 x. D Teeth of another specimen of about 

 the same size, about 7 x. E Dermal denticles of a female, about 678 mm. long, from Woods Hole, Massachu- 

 setts, about 22 X. F Caudal fin of Mustelus schmitti, 578 mm. long, from Muldonado, Uruguay (Harv. Mus. 

 Comp. Zool., No. 530), for comparison with M. canis. G Upper teeth of same, about j x. H Caudal fin of 

 M. tnento, 1,024 mm., from Payta, Peru. / Denticles of same, about 22 x. J Upper teeth of same, about 7 x. 



