Notes on certain Terrestrial Mollusca. 



167 



The general contour of P. Californica and P. Powellii, is 

 similar, but the latter has a slightly more tapering spire, and 

 its aperture is smaller in proportion than in the former. The 



Fig. It 



Fig. 12. 



P. Eowellii Newc. 



P. Californica Rowell. 



aperture of P. Powellii is narrower at the base, and the basal 

 tooth is longer and sharper than in P. Californica. The latter 

 has elevated rib-like strice, which are peculiar to it, and is the 

 only prominent character distinguishing it from P. decora 

 Gould. 



Succimca Sillimaiii, nov, sp. 



T. oblongo-ovata, tenuis, ruguloso-striata, nitidula, albida ? ; spira 

 brevis, acuta ; anfr. 3 convexi ; sutura iinpressa ; apertura obliqua, elon- 

 gato-ovata, superne angulata, basi efFusa ; columella leviter arcuata, 

 snperne filariter incrassata. 



Shell oblong-ovate, thin, coarsely striate, shining, whitish? 

 spire short, acute ; whorls 3, convex ; suture 

 impressed ; aperture oblique, elongate-oval, 

 angular above, effuse at the base ; columella 

 slightly arcuate, with a thread-like thickening 

 above. 

 Long. 20, diam. 8£ mill. ; Ap. 13 mill, longa, 

 medio 6 lata ; anfr. nit. 17i mill, longus. 



Fig. 13. 



Succinea Sillimani, 

 Bland. 



Habitat. — Humboldt Lake, Nevada. A single example 

 without epidermis, but fresh in appearance, was found and se'nt 



