170 THE CHICAGO ACADEMY OF SCIENCES. 
emptying into the Atlantic Ocean. Its northward extension to Lake 
Winnipeg is easily accounted for by the glacial Lake Agassiz and the 
Pleistocene connection of the Red River of the North with the Minne- 
sota River. Columella extends throughout the humid divisions of the 
Lower Austral, Upper Austral and Transition life zones and just over 
the border of the Canadian zone. 
GEOLOGICAL RANGE: Pleistocene. Goat Island Gravel Pits, Niag- 
ara River, N. Y. (Letson). This was the only record found referring 
to the geological range of columella. 
Ecotocy: Columella is an inhabitant of ponds and streams where 
the water is more or less stagnant; a locality with an abundance of 
lily pads is particularly favorable; it is found also along the shore in 
shallow water in the vicinity of cat-tails (Typha) and other reeds, 
upon which it is often found, mimicking the situs of the pulmonate 
genus Succinea. Rarely found in running water. Columella is a lover 
of shallow bays and small ponds or creeks, where it may browse in 
the pond scum and on bits of rotting stems of water plants. It has 
been collected by the writer associated with Lymnea stagnalis appressa, 
Galba obrussa and Galba palustris. Brook flowing from Crawford’s 
into seven-tree pond (Lermond, Maine). 
The following note is interesting, as it illustrates another of the 
almost unaccountable instances of distribution : 
“The L. macrostoma which I send you requires a note. It comes 
as near a case of spontaneous generation as anything within my ob- 
servation. It was found in a little pool about twenty feet in diameter, 
entirely cut off from streams and fed by a spring. I had for years 
frequented it for desmidia, etc., in which it was very rich. One season, 
and one only, appeared these Limnee, which do not occur elsewhere, 
as far as I now know, within twenty miles. The pond dried up that 
season and destroyed the locality.” (Dr. T. R. Ingalls in Binney, 
Rota) 
REMARKS: Columella may easily be known by its Succinea-like 
shell, resembling very closely specimens of Succinea ovalis Say. It is 
subject to considerable variation, especially in the height of the spire 
and in the size of the aperture; the whorls also vary in convexity. 
There is also some variation in consistency, some shells being heavy 
and thick, with a rather rough surface, while others are very thin, 
delicate and shining. The species is so unlike the other Lymnzas, 
however, that it need never be confounded with any species. 
A form (pl. XXIV, figs. 1-3) occurs in the southern states which 
is considerably smaller than ‘typical columella, averaging about two- 
