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. GonJobasis 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 and near Muncie. It is abundant in the big Vermilion below Middle 

 Fork. It has been identified by local naturalists as Goniohasis 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 livescens rather 

 than pulchella. Young and immature specimens are banded like Goniobasis 

 depygis Say. 



Goniohasis semicarinaia 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 small brook about two feet 



