266 THE CHICAGO ACADEMY OF SCIENCES. 
FLORENCIA FORMATION. : 
Ittinots: Indian Garden, Pecatonica River Valley, Stephenson Co. (Her- 
shey). 
VARIOUS PLEISTOCENE FORMATIONS. 
UNITED STATES. 
CALIFORNIA: Walnut Creek, Contra Costa Co.; Tassajora Lake Bed? 
deposit near Walnut Creek, Alameda Co., north of Livermore. (Cooper). 
Iowa: Drift of Iowa (Udden). 
Micuican: Near Buchanan, Berrien Co., with Mastodon remains (Smith) ; 
with Mastodon remains, Niles, Berrien Co. (Walker). 
NevapA: Upper Lahontan beds, Rye Patch, Humboldt Co. (Call). 
New Mexico: Dry Salt Lake, near Eddy, Eddy Co. (Sterki). 
Texas: Forks of Groesbeck Creek, three miles west of Quanah, Hardeman 
Cor: 
“Rush’s pasture, Wild Horse Creek, northeast of Big Spring, Howard 
Co., northwest Texas, from bed of sandy clay, twenty feet above present bed 
of creek. The bed rests upon a conglomerate composed of small silicious peb- 
bles. Found with mammalian remains” (Singley). 
BRITISH AMERICA, 
Ontario: Fossiliferous sands overlying the clays of Essex Co. (Stearns). 
Ecotocy: Modicella usually selects as a habitat a mud flat or a 
strip of muddy beach which is kept rather moist. In such a situation 
it has been seen by the writer in Wisconsin, Illinois, Indiana, New 
York and Pennsylvania. It has also been collected from boards, sticks 
and other debris along the shore. At Alpena, Michigan, it was col- 
lected by Dr. Nason on a broad, sandy beach near the outlet of Long 
Lake, in from six inches to a foot of water. The shells are very thick 
and well illustrate the effect of rough water. Mr. Woodruff records 
the habitat in southern Illinois as follows (Nautilus XI, p. 28): 
“The shells were found in a rocky glen or cleft in the center of 
the chain of high precipices known by the names of Fountain Bluff, 
Devil’s Bake Oven and Backbone. This cleft or ravine begins about 
three-quarters of a mile from the face of the cliff and gradually de- 
scends in a northwesterly direction until the bottom is reached, and 
one may stand upon a broad shelf of rock ten feet from the ground, 
with high overhanging cliffs of bare rock on both sides. A stream 
of clear spring water flows down this ravine and, falling over the high 
shelves of rock, has formed numerous round pools or basins. I was 
surprised to find no shells in the stream, and could only collect a few 
specimens of Limnea humilis, which I found clinging to the wet moss 
under the falls.” 
REMARKS: Modicella is closely related to humilis, differing in 
having a longer and narrower aperture and a less obese body whorl; 
in the majority of individuals the upper extremity of the lip where 
