TJic Loess of Xatchcz, Miss. — Shi nick. 28^ 
ly, too, such species are quite absent from the modern fauna 
of the uplands in and about Natchez, for there are no springs, 
or ponds, or swampy areas in which such snails as Physa, 
Liinnaca. etc., might thrive. It is true that aquatic species have 
been reported from this loess, but in all cases the reports are 
either indefinite, or refer to that which may not be loess. 
As early as 1846 Lyelh'' noted a deposit at Xatchez re- 
sembling loess and with "land, fluviatile and lacustrine shells 
of species still inhabiting the same country," luit he did not 
designate them by name. Later, discussing the loess of 
Natchez in the London Times f he said that the deposit "con- 
tains abundance of fresh water and land shells, of which I my- 
self obtained more than 20 species They belong to the 
genera Helix, Helicina, Pupa and Snccinca, accompanied or 
rather replaced in a few places where the loam passes into 
shell-marl by Lyninca, Plaiwrbis, Pliysa, Cyclas. . . . All 
species are indentical with Testacea, now inhabiting the same 
part of the U. S." The species of Helix, Helicina, Pupa and 
Succinea are, however, in no sense aquatic, and it will be ob- 
served that the deposit from which the shells of the species 
belonging to the aquatic genera Liinuaea, Planorbis, PJiysa 
and Cyclas (Sphaeriuui or Pisidium) were obtained is very 
doubtfully loess, — certainly not typical loess. Finally, in the 
Principles of Geology :■: Lyell says that this loess is "full of 
land-shell? such as Helix and Pupa, together with the 
amphibious genus Succinea, all of species novv' living in the 
same country. At a few points in the lower part of this for- 
mation, I observed shells of living species of Lymnea, 
Planorbis and Cyclas, — genera which inhabit ponds. . . . The 
only fossils of a truly fluviatile character which have been met 
with anywhere in this loess are the remains of three fish discov- 
ered lately (Alarch 19, 1866) by Colonel Green. They were 
found in the great platform of loess, two miles north of Mcks- 
burg, and only four feet below the surface, at the hight of 200 
feet above highwater mark." The genus Succinea cannot l)e 
properly designated as amphibious. It consists of two very 
distinct groups of species, to only one of which, represented by 
the species retusa {ovalis), the term may be applied, and this 
♦AtheiiEeum. Sep., 184G 
+ Dec. 8, 1846; reprinted in the Am. Jour. Sci. and Arts. 2nd series, 
vol. III. pp. 267-269, 1847. 
$Vol. I. p. 460, 1872. 
