Gyclostrema, Adeorbis, Vitrmella, and related genera. 123 



Vitrinella Tryoni sp. nov. 

 ? Vitrinella helicoidea Tryon, Manual, x, pi. 34, figs. 40, 41, 1888. 

 Plate XXII. figs. 11, 11 a, 



"A specimen from station 2278, off Cape Hatteras, N. C, in 16 

 fathoms, very closely resembles the figures in Tryon's Manual given 

 as v. helicoidea. 



It is a smaller, more transparent shell than the preceding, consist- 

 ing of about three flatly convex whorls, which lap well on to each 

 other, forming a very much flattened spire, and large body-whorl. 

 Suture inconspicuous, with an internal spiral line considerably below 

 it showing through the shell and indicating the width of the lapping 

 on of the whorls. Umbilicus moderate, deep, showing all the whorls, 

 with rounded walls, not defined by a carina as in V. helicoidea. 

 Unfortunately the lip is broken, but the general form of the aperture 

 is as in the preceding species, but with the columellar margin less 

 thickened. 



Greatest width, about 2""™; height, about -S"^"". 



Vitrinella diaphana (d'Orbigny). 



Rotella diaphana d'Orbigny, Histoire L'lle de Cuba, Moll., ii, p. 62; atlas, pi. 

 xviii, figs. 23-25, 1853. 



A specimen from station 2113, off Cape Hatteras, N. C, in 15 

 fathoms, very closely resembles the figures given by d'Orbigny as 

 Rotella diaphana. 



It is a minute, smooth, shining, opaque white shell consisting of 

 about three well-rounded whorls, forming a well-raised spire with 

 minute nuclear whorl and large body-whorl. Suture distinct. 

 Umbilicus rather small, deep, with rounded walls, showing only a 

 part of the whorls. Aperture as in Y. helicoidea^ but with the 

 columellar lip not only thickened but flattened and spreading slightly 

 over the umbilical region. Surface marked only by delicate micro- 

 scopic lines of growth. Greatest width, about i-g™"" ; height, about 



.gmm 



"Umbilical callus very minute," as given by d'Orbigny for this 

 species as well as for carinata, has doubtless led to their being 

 referred to Pseudorotella,^ Teinostoma and Ethalia. The thickened 



* Pseudorotella Fischer, Journ. de Conch., vi, p. 173, 1857 = P. pusilla {P&eSer) ; 

 Teinostoma Tryon, Manual, x, p. 104, 1888; Ethalia Dall, Bull. M. C. Z , xviii, p. 361, 

 1889. This species seems to have been referred also to Cyclostrema by Poulsen. 



