418 PROCEEDINGS OF THE ACADEMY OF [April, 



Another specimen has the height 10, diam. 7 mm., and is composed 

 of 9 whorls. It shows more of the brown and less of the white color. 



The extreme variability of P. cupula leaves it debatable whether 

 this may not be a dwarf race of that species. 



No specimens of this form were found last summer, and it is through 

 the courtesy of Dr. William H. Dall of the National Museum, that I 

 am able to describe and figure it. The specimens came to him without 

 labels, so that we are left to conjecture their age. The slender specimen 

 is so glossy and brightly colored that Dr. Dall doubts whether it can 

 be a fossil, but it seems to me the simpler hypothesis to suppose that 

 it was preserved in the sand in the same manner as the type of P. nelsoni 

 callosus, which it so closely resembles in color and polish. The shell 

 sand seems to be a complete protection from destructive agents. On 

 this hypothesis it had originally about the color of Pcecilozonites ber- 

 mudensis. 

 Pcecilozonites bermudensis Pfr. 



Pilsbry, Proc. Acad. Nat. Sci. Phila., 1888, p. 289; 1889, p. 85. 



The typical variety seems to be of recent origin. It is distinguished 

 from the fossil by a less rounded upper surface, less flattened apex, 

 larger umbilical perforation, and usually smaller number of whorls. 

 My largest specimen I found on Rabbit Island, Harrington Sound, 

 buried under drift sand at some time previous to the cultivation of 

 the island. It measures alt. 13, diam. 24.5 mm. The largest and 

 smallest living mature shells measure as follows : 



Alt. 14.5 Diam. 20. mm. 

 14 22 



10 16.5 



An average fully adult specimen measures : 



Alt. 11 Diam. 20 Umb. 1.7 mm. 



and has a trifle more than 7 whorls. 

 Pcecilozonites bermudensis var. zonatus Verr. PI. XXXVI, fig. 3. 



This differs from the type of the species in possessing an almost 

 uniformly curved upper contour line, an almost flat apex, and a more 

 constricted umbihcus. The keel is distinct, as in the recent form. 

 Whorls 7f . The aperture is surrounded by callous thickenings as in 

 P. nelsoni callosus. Alt. 13.5, diam. 23, umb. 1 mm. 



Specimens come from localities Nos. 806, 808, 814, 816 and 809. 



The extremes from locality No. 808 are : 



Alt. 16 Diam. 22.5 mm. 



15 25 



12.5 20.5 Umb. 1 mm. wide. 



