Loess of lozua City — Shiuick. 355 
Physa sayi Tap. 
Quite commjon locally. None fossil. 
Planorbis campanulatus Say. 
Rare locally in ponds. None fossil. 
'''Planorbis trin'olvis Say. 
Very common in shallow ponds. Reported from Mis- 
souri, but, if occurring at all, certainly not common. 
*Planorbis bicarinatus Say. 
Common in shallow ponds. One fossil specimen was 
collected by Prof. Beyer at Ames, and the species has been 
reported from the loess of Tennessee.* 
Planorbis exacutus Say. 
Lccially common in shallow ponds. 
^Planorbis parvus Say. 
Yevy common in ponds, etc. Rare in the western loess. 
""Planorbis albus AlncU. 
Quite rare in rather more permanent ponds. Prof Ud- 
den collected one specimen in the loess of Milan, 111. 
Planorbis dilatatus Gld. (?). 
Locally rather frequent. None fossil. 
*Segmentina armigera (Say) H. & A. Ad. 
Common in ponds. Rej^orted from the loess of Missouri, 
but not known as a fossil in Iowa and Nebraska. 
Ancylus diaphanus Hald. 
Common on sticks, etc. in more permanent ponds. 
*Valvata tricarinata (Say). 
Quite common. It also occurs in deeper ponds. Prof. 
Udden collected it in the loess of Milan, 111., and it is re- 
ported from Missouri. It is, however, very rare as a fossil. 
PisiDiuM compressum Prime (?). 
A few valves of this, or a closely related species, were 
found in the local loess. The species is now common, es- 
pecially westward, in small prairie streamlets, etc. 
All but the last two species in this list are air-breathing 
forms. The last one is a bivalve. 
h. Species of deeper ponds, bayous, etc. 
GASTEROPODS. 
BiTHYNELLA OBTUSA (Lffl) St. Quite common. 
Amnicola cincinnatensis (Anth.). Very common. 
*Safford, Geology of Tenn , p. 434-, 1869. 
