88 



THE NAUTILUS. 



1-18 feet deep. It was dredged in great abundance on a mud 

 bottom covered with Cladophora fracta, in 8^ feet of water. 

 Many immature individuals occur with the adults. 



Amnicola oneida Pilsbry. This is the narrowest species in 

 the lake, greatly resembling Amnicola lustrica but being more 

 slender. It was first seen in 1915 in a lot of shells from French- 

 man Island 1 but only one specimen was secured. It occurs on 

 all varieties of bottom and in all depths of water from one and 

 a half to 15 feet. It is not common on boulder or gravel bot- 

 toms, but on sand, clay, and mud bottoms, where there is a 

 covering of filamentous algae ( Cladophora, Oedogonium or Spi- 

 rogyra) in 2h to 4 feet of water, it is the commonest mollusk in 

 the region. In one or two dredgings it was found in abundance 

 in 8-9 feet of water but it is not usually plentiful in deeper 

 water. Many young and immature individuals were collected 

 with the adults. 



Amnicola clarkei Pils. This small, subacute species was found 

 associated with bakeriana in four places, though it is not as 

 abundant as that species. Occurs on sand, cla} T , and mud 

 bottoms, in water 3-8J- feet deep, usually in filamentous algae. 



Amnicola emarginata (Kiister). This characteristic species 

 occurred sparingly in water from 10-18 feet deep on mud and 

 gravel bottoms, usually with the filamentous algae Cladophora 

 and Spirogyra. 



Pleuroceridae. 



Goniobasis livescens (Menke). Found only on boulder and 

 gravel bottoms, on exposed shores or points, in water one and 

 a half to four feet deep. Most abundant in water 1-3 feet deep 

 on a boulder shore. Many young and immature individuals 

 occur. The species as it is found in Lower South Bay varies 

 in the obesit}^ of the body whorl, narrow forms occurring, some 

 with faint bands resembling the shell from Illinois called depy- 

 gis. The columella is deeply tinged with purple. Several 

 young individuals were collected having strongly keeled whorls 

 and measuring 16 mm in width and 7 mm in width. 



l See Technical Bulletin, IV, page 269, fig. 45, No. 21. 



