124 THE NAUTILUS. 
‘‘ Amnicola egena” of Gould being a spiueless Potamopyrgus from New 
Zealand. 
Descriptions of New Species. 
Paludestrina imitator, ». sp- 
Shell narrowly perforate or nearly closed, narrowly ovate, thin, 
light corneous, subtranslucent, nearly smooth, not glossy; whorls 43, 
the first planorboid, causing the apex to be decidedly obtuse, the rest 
quite convex, separated by a deep suture. Spire slender, conic. 
Aperture somewhat less than half the shell’s length, ovate, angular 
posteriorly, the parietal margin somewhat flattened; peristome thin, 
the inner margin adnate tothe preceding whorl for a short distance 
above. Alt. 3, diam. 1.6, greatest axis of aperture 1.28 mm. 
Counties near San Francisco Bay, California. Types from Santa 
Cruz. 
This species, though corneous and subtranslucent, resembles a young 
Bythinella nickliniana in form. It is evidently a ecmmon shell in the 
region mentioned above. In a lot from Oakland the shells are larger 
length 43 mm, with five whorls. This is analagous to the attenuata 
form of nickliniana, in the East. The same large form is before me 
from Petaluma Creek, Sonoma county (J. B. Davy) and Santa Cruz in 
brackish water (W. J. Raymond); and [I have seen similar but 
deeply eroded specimens, the earlier whorls wholly removed, from San 
Pedro. It may be that the types and other specimens before me of 
small size, perhaps some 200 shells in all, are only half grown, and all 
would attain a length of 4 to 5mm. when adult. It is conspicuously 
unlike “ Bythinella intermedia” Vryon and Pomatiopsis binneyi Tryon, 
and is less attenuated than the smooth * seemani”’ form of ** Tryonia”’ 
protea. P. stearnsiana is not attenuated above, but stout spired, more 
on the style of P. longinqua Gld. (intermedia Tryon), while in imi- 
tator the spire is slender above, though the apex itself is quite obtuse. 
P. stearnsiana, n. sp. 
Shell narrowly perforate, ovate, thin, corneous, nearly smooth, some- 
what glossy, whorls nearly 44, convex, separated by rather deep sutures, 
the spire with convexly conic lateral outlines, stout. Apex rather 
obtuse. Aperture half the shell's length or somewhat less, ovate, the 
posterior angle blunt and rounded, peristome continuous, the inner 
margin weil defined, generally quite free at the edge from the adjacent 
whorl. Alt. 2.6, diam 1.7, or larger up to 3.2 mm. alt. 
Near Oakland (type locality); Marshall’s, Marin Co.; Tuolumme 
Co. (Hemphill). San Franciseo Peninsula? (G. W. Dunn.) 
