I have omitted most of the compound terms used by authors to describe the forms or 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. “Striæ” 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 found 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.
Note.—The * indicates the original measurement of authors, in hundredths of an inch.
A. Shell with edge of mouth sharp.
Fam. Helicellidæ. Shell corneous, thin, polished, translucent, sometimes with internal teeth.
Subfam. Vitrininæ. Shell very fragile, whorls 2 or 3, the last greatly expanded, not covering the animal.