1. GENERAL MORPHOLOGY OF THE LYMN/EAS. 
1. THE SHELL (PLATE II, FIGURE A). 
The SHELL in the Lymneeids is typically elongated, with a pointed 
spire and more or less turreted whorls. The shell may be as thin as 
paper, (haldemam, columella) or, thick and solid (megasoma, cock- 
erelli). It is usually higher than wide. The whorls are tightly coiled 
about a central axis, forming a characteristic columella. The contour 
of the shell varies from distinctly globose (sonomensis, emarginata 
wisconsinensis) to very much elongated (haldemani, reflexa). This 
varying contour is well shown in several species, two of which are 
mentioned below. 
Elongated. Depressed. Globose. 
bulimoides techella bulimoides cockerelli bulimoides cockerelli (typi- 
(var.) cal). 
emarginata canadensis emarginata mighelst emarginata wisconsinensis 
The shell is normally dextral in America, but in the Hawaiian 
Islands several sinistral species occur. Rarely a sinistral individual, 
will be found, one such having been seen in the collection of Mr. Henry 
Hemphill (Galba obrussa), and one in the collection of Dr. W. A. 
Nason (palustris). 
SizE: The size ranges from the tiny Galba dalli, which is 4 
millimeters in length, to the giant Lymnea stagnalis, which attains a 
length of 60 millimeters. 
The Spire (1) varies in the different species, in many being acutely 
pointed and elongated, in some acute and depressed, in others broadly 
dome-shaped and in a few flatly depressed. All gradations occur be- 
tween these extremes. 
Tue WuHorts (3) may be very flat sided, as in evilis and halde- 
mani, or very convex and obese as in techella cockerelli and emarginata 
wisconsinensis. The SuTuREs (4) vary accordingly, being just per- 
ceptible in some species (/aldemani) and deeply impressed or even 
channeled in others (auricularia, randolphi). 
The APERTURE (2) is usually ovate, elongate-ovate or rounded, 
but in a few species is much elongated and narrow. There are no 
teeth or other obstructions, but a strong plait is frequently developed 
on the columella. The aperture may be long and narrow, with parallel 
