IOWA ACADEMY OP SCIENCES. 
Ill 
Iowa, than exists to-day between the surface conditions of the 
same regions. This fact is irrefutable, and must not be over- 
looked in any discussion of the conditions under which loess 
was deposited. 
TABLE OF SPECIES.' 
B 
0 
D 
E 
F 
G 
H 
1 
J 
K 
L 
M 
N 
o,p 
Q 
R 
S 
T 
55 
157 
210 
12 
5 
5 
1 
81 
8 
17 
89 
21 
9 
14 
3 
3 
1 
12 
1 
14 
1 
96 
45 
1 
1 
..1 
12 
6 
70 
+ 
¥ 
2 
16 
4 
7 
6 
1 
2 
3 
1 
2 
1 
1 
21 
"2 
280 
63 
3 
1 
1 
17 
2 
3 
14 
1 
i 
4 
1 
12 
1 
9 
3 
1 
1 
2 
4 
i2 
2 
3 
2 
127 
1 
10 
3 
28 
18 
1 
4 
3 
27 
10 
1 
1 
1 
12 
10 
‘i 
22 
3 
1 
2 
i" 
1 
1 
1 
4 
'2 
1 
12 
1 
1 
5 
10 
4 
21 
‘2 
3 
1 
2 
2 
4 
20 
18 
180 
11 
6 
19 
46 
6 
935 
16 
’3 
8 
i 
i 
10 
1 
4 
21 
7 
235 
7 
1 
i 
58 
1 1 
3 
11 
28 
5 
279 
11 
‘3 
2 
2 
1 
7 
1 
24 
13 
250 
14 
1 
4 
4 
2 
1 
1 
i 
3 
8 
72 
2 
21 
1 
12 
3 
5 
2 
4 
4 
2 
2 
15 
3 
3 
15 
5 
Helicina occulta Say 
Vallonia gracilicosta Reihn 
Vallonia parvula Sterki 
Vallonia perspectiva Sterki 
Polygyrcb mulUlncata (Say) Plls . 
Polygyra profunda (Say) Pils — 
Polygyra hirsuta (Say) Piis 
Polygyra leai (Ward) Piis 
Strobilops Virgo Pils 
Lcuchochila fallax (Say) Try 
Bifldaria armifera Say) St 
Bifidaria contracta (Say) St 
Bifidariaholzingcri (Sterki) St. . . 
Bifidaria curvidens (Gld.) St 
Bifidaria pmtodon (Say) St 
Pupa blandi (Morse) Blnn 
Vertigo boUesiana Morse 
Cyochlicopa lubrica (Miill) P. & J. 
Vitrea hammonis (Strom) P. & J. 
Vitrea indentata (Say) P. J — 
Conulus fulvus (Drap.) Miill 
Zonitoides arboreus (Say) St 
Zonitoides sMmekii (Pils) P.& J. II , 
Zonitoides minusculus (Binn.) P. 
& J 
Pyramidulaalternata (Say) Pils. . 
Pyramidula striatella(Anth.) Pils 
Helicodiscus lineatus (Say) Morse 
Succinea obliqua Sayt | 
Succinea grosvenorii Lea ( • ' ' 
Succinea avara Say 
lig-g- of a land snail 
*The nomenclature of Pilsbry and Johnson’s recent Catalogue of the Land Shells of 
N. Am is here employed. As there are .some departures from former usage, the 
changes are here noted : 
Species 2, 3 and 4 were formerly included under V. pulchella. 
Species 5 and 6 were referred to the genus Mesodon, and 7 and 8 to Stenotrema. 
Species 9 was included under Strobila labyrinthica. 
The species of Leuchochila and Bifldaria were included in Pupa. 
Species 18 was called Ferussacia subcylindrica. 
Vitrea, Conulus and Zonitoides were formerly placed in the genus Zonites, and No. 19 
was called Zonitoides radiatulus. 
Pyramidula was formerly Patula. 
Succinea grosvenorii was called S. lineata. 
tone specimen of P. profunda was found by the writer in exposure 0 (since con- 
siderably altered) in 1890. 
■4:Three specimens of this species were collected in exposure 0 in 1890. 
IIThe writer formerly regarded this as a form of Zon, nitidus. Mr. Pilsbry, however, 
regards it as distinct, and in deference to his opinion his name is retained. 
HThe form of S. obliqua which occurs most commonly in the loess is the narrower, 
smaller form with more extended spire, such as is not uncommon (living) in Iowa and 
as far east as Indiana. As it is difhcult to distinguish between some forms of this and 
S. grosvenorii, the two species are not here separated, as more time for careful compari- 
son of the large sets will be required. 
