LYMNAZIDZ OF NORTH AMERICA. 21 
LYMN#ZA STAGNALIS LILLIAN Baker. Plate LV, figure 2. 
Stagnalis appressa lives in quiet waters but this race, characterized by the 
shortened up spire and large aperture, is an inhabitant of exposed lake shores 
where it is frequently subjected to very rough usage by the heavy seas caused 
by storms and high winds. In Tomahawk Lake, Wisconsin, this race lives on 
a sandy shore fully exposed to the violence of the waves. In Isle Royale, in 
Washington Harbor, Lymnea stagnalis sanctemarieé is found attached to the 
rocks, and is not readily removed by the waves.’ 
This race (stagnalis lilian@) has been produced by the change of environ- 
ment from the quiet waters of protected bays to the rough waters of lakes. A 
parallel case may be cited in the palustris of Alpena, Michigan, where a change 
of habitat from quiet, marshy waters to the exposed pools of a lake beach has 
produced a quite distinct race. 
GALBA EMARGINATA WISCONSINENSIS Baker, also lives on an exposed beach 
in the Wisconsin lakes, associated with stagnalis lilliane. 
GALBA WoopRUFFI (Baker). Plate LVI, figure 1. 
At Millers, Indiana, this species is found abundantly on a sandy beach, 
fully exposed to the violence of the waves. Although no living specimens have 
been found, it is probable that the species lives not far from shore, as the dead 
shells are found in abundance all along the southern shore of Lake Michigan. 
Associated with this Lymnzid are species of Spherium, Valvata, Amnicola and 
Lampsilis. 
GALBA CATASCOPIUM (Say). Plate LVI, figure 2; LVII, figure 1. 
This species is typically an inhabitant of the shore of quiet rivers or lakes 
where it may browse among the alge along the shore. In the Genesee River and 
in the Erie Canal (figure 2) at Rochester, N. Y., this species may be found 
by countless thousands along the quiet shores of these streams. Some forms, 
by change of habit to the exposed shore of a large lake or bay, as at Pine 
Lake, near Charlevoix, Michigan, have developed a smaller, more solid shell 
than those individuals inhabiting the quiet areas mentioned above. Along the 
shore of Lake Ontario, where pools of water have collected behind breakwaters 
(due to rough water), this species lives in large numbers on the mud flats in 
shallow water (pl. LVII, fig. 1). In the Delaware River, catascopium lives 
between tides and is subject to all the influences of the littoral marine species. 
GALBA PALUSTRIS (Miller). Plate LVII, figure 2. 
Palustris is characteristic of stagnant ponds and swampy pools, where 
there is a quantity of vegetation, both living and dead. The edge of a Typha 
latifolia plant society is almost always a favorite resort of this species (pl. LV, 
fig. 1). 
PSEUDOSUCCINEA COLUMELLA (Say). Plate LVIII, figure 1. 
This fragile Lymnza lives in a quiet, stagnant habitat, usually among cat- 
tails (Typha). The surface of the water is usually covered with pond scum 
(Spirogyra) or other floating vegetation. A pond filled more or less with lily- 
pads also affords a typical habitat for this species (pl. LIII, fig. 2). 
When the habitat is a rapidly flowing stream, the shell tends to 
become solid and to produce a large aperture to enable it to withstand 
1c, f. Adams, Ecol. Surv. Mich., p. 97. 
