60 ILLINOIS BIOLOGICAL MONOGRAPHS [158 
from a post-glacial fossil deposit. None were found either alive or dead 
in any other part of the Big Vermilion examined, excepting the two speci- 
mens mentioned above. 
In the Sangamon River, at Mahomet, elevatum is very abundant on a 
sandy bottom in water a foot in depth (low water period). The speci- 
mens are large (maximum length 35 mm.) and vary in color from light yel- 
lowish to black or dark chestnut with a light zone below the suture. The 
characteristic peripheral keel is developed on the majority of specimens 
and ascends the spire just above the suture. In a few individuals this keel 
is absent and the body whorl is rounded. Many intermediate forms occur 
connecting these rounded shells with the more distinctly keeled forms. 
Usually there are from one to six spiral ridges on the base of the shell extend- 
ing longitudinally parallel with the peripheral keel. The strongly carinate 
whorls of the young shell are six in number and these lose their sharpness 
more or less abruptly on the seventh whorl. No individuals were seen in 
which the protoconch or nucleus of the first whorl was preserved. Young 
and half-grown specimens have two brown bands on the spire whorls and 
four bands on the body whorl and base of the shell. This species also occurs 
in the Sangamon at White Heath, and it has been found in several Pleisto- 
cene deposits near Mahomet, the white shells of the fossils being washed 
out of the bank by periods of high water. 
48. Goniobasis livescens Menke. 
This river snail occurred in but four places in Salt Fork. It was 
infrequent at bench mark 655 and abundant just below the dam at Homer 
Park andnear Muncie. It is abundant in the big Vermilion below Middle 
Fork. It has been identified by local naturalists as Goniobasis pulchella 
Anthony and has been reported as this species by other students as from the 
Big Vermilion River (Baker, 1906:98). Specimens were sent to Mr. Calvin 
Goodrich, who is making a study of this family, and were identified as 
livescens. I quite agree with Mr. Goodrich that they are /ivescens rather 
than pulchella. Young and immature specimens are banded likeGoniobasis 
depygis Say. 
Gontobasis semicarinata Say is reported from the Big Vermilion River 
by Marsh (Baker, 1906:98) but no specimens have been seen from this 
stream. The species may live in the river below Danville or the citation 
may be based on long-spired livescens. 
FAMILY AMNICOLIDAE 
49. Pomatiopsis lapidaria (Say). 
This tiny snail is abundant in small, cold streams flowing into the 
Sangamon River. At one locality, about three-fourths of a mile below 
Mahomet, it was extremely abundant in a smal! brook about two feet 
