326 PYEAMIDELLIDiE. 



Pijrnmis fiisra, Adams, Bost. Joiirn. Nat. Hist. ii. 282, pi. 4, fig. 9. 



Jamhiiu fused, Adams, Ibid. iii. 337. 



Odostomia fasca, Gould, Iiiv. 1st cd. 270, fig. 176. — Stimpso.v, Check Lists, 5. — De 



Kay, N. Y. Moll. 116, pi. 36, tig. 342. 

 Chemnitziafusca, Stimpso\, Shells of New England, 41. 



Shell small, thin, elongated-conical, rather blunt, or A^orn off at 



apex, a smooth and glossy violet-brown epidermis covering it, 



through which the lines of growth are perceptible : Avhorls 



Fig. 594. . II' 



SIX, probably eight when the tip is entire ; slightly convex, 



regularly tapering, and separated by a well-defined suture, 



'■ and sometimes by a revolving line just below it, so that the 



suture seems double ; aperture ovate, widened at the middle 



O. fusca. . „ . 



by a twist of the pillar lip, acutely angular behind ; simple 

 and sharp, widely and regularly rounded in front ; it ascends upon 

 the columella, and forms an oblique, nearly transverse ridge, as it 

 revolves within the aperture, and so deep as to be nearly concealed ; 

 space between this fold and the posterior angle of the aperture 

 joined by a thin plate of enamel ; an umbilical indentation about 

 the middle of the left lip. Length, five twentieths of an inch ; 

 breadth, three fortieths of an inch ; divergence, twenty-six degrees. 



This shell was first found by Professor C. B. Adams, at New Bed- 

 ford, clinging to planks, not far al)ove low-water mark, and from 

 him I received my specimens. They have since been found at 

 Dartmouth and Tiverton. 



Compared with O. bis/ifii rails, with which shell it is most likely to 

 be confounded, it is shorter and more blunt-pointed ; the whorls 

 are more flat, and the lowest in exact keeping with the rest ; the 

 color very much darker ; the aperture is broader and modified by a 

 twist of the left margin, without any prolongation at Ijasc. The 

 turning of the lip into the aperture forms a fold, which, in some 

 specimens, is not seen without looking far within : in others it is 

 quite conspicuous, and in others it is even divided by a furrow into 

 two folds. The figure and description in the " Boston Journal of Nat- 

 ural History" were drawn from specimens much smaller and less per- 

 fect than some since found ; so that they are both imperfect. The 

 spiral ridge or fold on the columella is there said not to exist at all. 



These last two shells differ in some characters from the follow- 

 ing, and perhaps belong to a different genus. The shell is thin and 

 horny, the aperture regularly rounded in front, and the fold on the 

 pillar inconspicuous. In the true Odostomia; the shells are of a 

 solid, ivory structure, and the lip somewhat produced in front, form- 

 ing the connecting link with Cerilhium and the Canallfera. 



