MARGARITA. 287 



MIDDENDORFF, Mai. Rossica, ii, p. 69. M. helicina Fabr., KRAUSE, 

 Archiv f. Naturg. 1885, p. 262. 



This species is very abundant. It may be known by the smooth 

 surface, lightly spirally striate around the umbilicus, the rather 

 narrow umbilicus, etc. 



T. borealis Phil, was proposed for American specimens ; Phil- 

 ippi's figures are copied on PI. 39, figs. 49, 50. His figure of 

 T. margarita Mont, on PI. 39, fig. 63. M. vulgaris Leach (PI. 39, 

 fig. 46,) is the same as the form called campanulata by Morse. 



M. grcenlandica ' Beck ' of Sowerby, in Reeve, f. 6, and of Philippi, 

 Conchyl. Cab. t. 37, f. 5, are probably additional synonyms of this 

 protean species. The figures of Sowerby and of Philippi are copied 

 on PI. 44, fig. 22, and 21. 



M. ACUMIXATA Sowerby. PL 39, fig. 55 ; pi. 66, fig. 6. 



Shell orbicular, thin, whitish ; spire acuminate, whorls 5, rounded, 

 smooth ; suture distinct ; aperture orbicular ; umbilicus small. 



Alt. '55, diarn. '5 in. (Sowb.'j 



Arctic Ocean. 



M. acuminata SOWB., Mai. and Conch. Mag. i, p. 26 (1838). 

 Conch. 111., f. 7. SOWB. JR. in Reeve, Conch. Icon., f. 13. Trochus 

 bembex PHIL., Conchyl. Cab., p. 286, t. 42, f. 5. M. acuminata 

 MIGH. & AD., Bost. Journ. N. H. iv, p. 46, t. 4, f. 15. 



The M. acuminata Mighels and Adams (pi. 66, fig. 6), taken in 

 the Gulf of St. Lawrence, is described as follows : 



Shell small, orbicular, subconical, thin, of a grayish-white or 

 russet color , spire acuminate ; whorls 4, well-rounded, smooth, 

 covered with a thin semitransparent epidermis, striae of growth very 

 fine and compact ; suture well impressed ; aperture orbicular, 

 considerably oblique, beautifully iridescent within ; operculum 

 horny, spiral. Alt 6J, diam. 6? mill. (M. & A.) 



The single specimen of this American form before me is much 

 more depressed than the figure given by Sowerby. It seems to be 

 specifically distinct. 



M. VAHLII Moller. PI. 39, figs. 58, 59. 



Shell small, conoidal, very smooth, shining, hyaline, pearly ; 

 whorls 4-4 J, convex, the last subangular ; umbilicus narrow. (Phil.~) 



This is the smallest of the Margarita species known to me. The 

 shell approaches a pretty flat cone in form, for the upper whorls are 



