334 PROCEEDINGS OF THE CALIFORNIA 



fication, and the selection of names applicable to them as genera, is a difficult 

 task. To undertake to distinguish genera by the lingual teeth, mucous pores, 

 or any other single character of the soft parts, is less practicable than to do it 

 by the shells alone, and little if any more reliable. There may, however, be 

 foreign shells closely resembling ours in form, which must still be separated on 

 account of the animal. 



I have omitted most of the compound terms used by authors to describe the 

 forms of shells, as they are not used with any uniform system, and do not well 

 define the differences between the various species of the same group. The 

 dimensions are more reliable for separating allied forms. " Striae "is also an 

 indefinite term, used by various authors for lines of growth, revolving grooves 

 or stripes of color, and is therefore never used alone in this article. 



It is remarkable that no reversed species or variety has yet been fouud west 

 of the Rocky Mountains. 



Order PULMONIFERA. 



Mollusca with or without shells, breathing by lungs, inhabiting the land, 

 fresh or salt waters. 



Subord. Geophila. 



Terrestrial Molluscs. Section with external rounded shells. 

 A. Shell with edge of mouth sharp. 

 Fam. Helicellidce. Shell corneous, thin, polished, translucent, 

 sometimes with internal teeth. 

 Subfam. Vitrinince. Shell very fragile, whorls 2 or 3, the last 

 greatly expanded, not covering the animal. 

 I Genus Binnkya Cp. Ear-shaped, nearly flat, one-third the length 

 of animal, spire none, corneous. 



1 notabilis Cp. Whorls 2, pale brown, first with 30 delicate revolving 

 ribs, epidermis expanded ; diam. * 0.46, alt. 0.12 in. 



H Genus Vitrina Drap. Depressed subglobose, last whorl very 

 large, swollen, imperforate, shining. 



2 Pfeifferi Newc. Wh. 3, greenish white, suture finely margined, colu- 

 mella arched, spire flattened, diam. * 0.19, axis 0.09. 



Subfam. Helkellina. Shell thin, translucent, whorls 4 to 6, mouth 

 moderate, surface smooth, pitted below or perforated. 



III Group. Hyalina Feruss. Depressed globose, moderately umbili- 

 cate, or pitted, vitreous, shining, whorls uniform. 



3 Breweri Newc. "Wh. 5, pale corneous, umbilicus large, suture slightly 

 channeled, aperture lunar ; diam. *0.20, axis 0.10. 



IV Group. Macrocvclis Beck. Discoid, widely umbilicate, growth 

 lines often coarse, last whorl usually deflexed. 



4 Mewberryana W. G. Binn. AVh. 6, reddish-brown, flattened, mouth 

 not deflexed, fine revolving striae ; diam. 1.43, axis 0.50. 



Note.— The * indicates the original measurement of authors, in hundredths of an inch. 



