The Loess of Xatchez, Miss. — Shiniek. 293 
are likely to be found in the northern loess. The remaining 
twenty-four of the species listed in the table of fossils have all 
been fotuid more or less abundantly in northern loess. 
Several additional points of interest are presented by some 
of the Xatchez fossils. Only two of the shells of Polygyra tliy- 
roides buccitlenta have the parietal tooth. The remaining 
edentate specimens somewhat simulate P. clausa, but they are 
less elevated, and not so heavy nor so coarsely striate as the 
shells of that species. The parietal tooth is easily broken ofif 
in the fossils of this and other species, and in identifying fossil 
species too much importance must not be attached to its ab- 
sence. 
The fossil Polygyra hirsiifa is the small form, approaching 
maxillatniu, which is the common form in the south. Polygy- 
ra uionodon is the form usually named Icai, and P. monodon 
fraterna is the form generally known as typical monodon.''^ 
The modern shells and the two fossils are of the 'leal' type, 
but have a smaller umbilicus than the northern form. !Most of 
the fossils are of the larger fraterna type. It was at first 
thought by the writer that the fossil shells of Gaslrodoiifa'uiiil- 
tideiitata might be G. lauiellidens Pilsbryf, but a careful ex- 
amination of the teeth shows that the fossils are without 
doubt G. inultidentata. Modern G. iiiiiltidcntata is reported 
from southeastern Tennessee by Ferriss. t 
Fossil Pyraniidiila alfeniata and var. costata are not always 
sharply distinguishable, but the specimens listed as costata all 
show more or less clearly the coarse ribs which characterize 
this southern variety. 
Snccinca oralis Say is the species well known as S. ohli- 
qiia. § The snails' eggs could not be identified, but they are 
undoubtedly eggs of land snails. Two species were collected. 
The Natchez loess is of special interest because it furnishes 
particularly weighty arguments against both the aqueous and 
glacial theories of the origin of the loess. That this loess is 
not of aqueous origin is shown by its fossils, which are terres- 
trial upland species, and by its distribution over a high ridge, 
higher than the surrounding country for many miles around. 
*Oii authority of Pilsbiy.— Proc. Acad. Nat. Sci. Phil, for 1900,— 
po. 454-.5. 
See Nautilus, vol. XI, p. 134. 
J Nautilus, vol. XIV, p. 58. — 1900. 
gSee The Mollusca of Chicago Area, Frank C. Baker. — Bull. Chicago 
Acad. Sci., no. Ill, pt. 2. » 
