TURBINA'CEA. MOLLUSCA. MARGARITA. 253 



tially covering it ; a very thin stratum of enamel sometimes extends 

 across the body of the shell ; throat within, with lines correspond- 

 ing to the external marking ; operculum circular, multi-spiral. 

 Height I inch, base a little less. 



Found in a very fresh and beautiful condition, but rather rare as 

 yet, in the stomachs of fishes caught in Massachusetts Bay. 



It is distinguished by the beautiful, sharp lines of growth, which are 

 not interrupted by the spiral ridges, and by these ridges covering all 

 the base ; also, by the slight projecting angle of the aperture. It is very 

 closely allied to M. striata^ Broderip and Sowerby, " Zool. Journ.," iv. 

 371, and figured in Sowerby's " Conch. lUust.," (Margarita) fig. 3. By 

 the kindness of Mr. Sowerby, however, I have been enabled to com- 

 pare the two. In M. striata the whorls are not angulated by the re- 

 volving lines, the largest of which are not larger than those on the 

 base of our shell, while its base is nearly smooth ; its umbilicus is 

 much smaller. In color, size, and general shape, the shells are alike. 



Margari'ta obscu'ra. 



/S/ieZZ depressed-conical, solid ; spire obscure, reddish-hrown, base 

 ash-colored ; ivhorls angulated by two or three revolving ridges ; 

 lines of growth coarse; aperture circular, pearly within. 



Figure 161. 



State Coll., No. 33. Soc. Cab., No. 2279. 



Turbo obscurus, Couthouv ; Bost. Journ. Nat. Hist., ii. 100, pi. 3, f. 2. 



Shell small, solid, orbicular, low-conical, of a dull reddish- 

 brown above, and of a light ash-color at base ; whorls five, con- 

 vex, and rendered angular about the middle by a prominent re- 

 volving ridge ; on the lower whorl are often one or two less con- 

 spicuous ridges, and numerous very fine lines ; on the base these 

 are so faint, as to be usually imperceptible without a magnifier ; 

 these, with rather coarse lines of growth, somewhat prominent at 

 intervals, often produce an indented or cellular appearance on the 

 surface ; umbilicus large and deep, bounded by a sharp, angular 

 ridge ; aperture circular ; lip simple and sharp ; within iridescent ; 

 operculum horny, multi-spiral. Height ^^-^ inch, diameter of base 

 aV inch. 



Found rather plentifully in fishes caught off Nahant. 



