20 
Length, three inches; heighth, one-and-a-half, 
and breadth, one-and-a-quarter inches. 
This species like the preceding, is of South- 
ern distribution, was found by Say, in South 
Carolina, and described in the Journal Acad- 
emy of Natural Sciences, Philadelphia, in 1822. 
A few specimens were taken at the same time 
and place, with P. costata, at New Bedford, by 
Mr. Greene. Perkins says “it is not rare at 
New Haven, where it is found in peat bogs, 
and in clay, at high water mark.” It was first 
found in Rhode Island, in mud, brought up by 
the dredger, in deepening the channel of Pro- 
vidence River. There is a large bed of them 
in clay, near Field’s Point, two miles south of 
Providence, and they are common at Bristol, 
and probably in many other places in Narra- 
gansett Bay. 
To be Continued. 
BRIEF NOTES ON THE LAND AND 
FRESH-WATER SHELLS OF MER- 
CER CO., ILL. 
BY WILLIAM A. MARSH. 
(Continued. ) 
48.—Margaritana confragosa, Say. 
Shell plicate; quadrate in outline. The 
epidermis of this species varies from dark green 
to dark brown. ‘This is our most beautiful 
Margaritana, and being everywhere rather 
rare, it is our most desirable shell for exchange. 
It is very much plicated and much. inflated. 
with incurved beaks having a deep furrow over 
their summits, and highly ornamented with a 
row of sharp tubercles on each side. The dark 
brown varieties are ornamented with a dark 
band running around the shell with the growth 
lines. This species has a white nacre, and is 
provided with heavy, solid teeth. It is a very 
constant species with the exception of the color 
of its epidermis, and cannot be easily con- 
founded with any other. It is found only in 
our river sloughs haying a muddy bottom, 
where the water is still. Up to seven years 
ago, I had found but two or three of this 
species, but, for some unknown reason, in the 
very localities where formerly I looked for it in 
4 
| straight and parallel with its hinge line. 
| species is covered with beautiful green rays 
THE - CONCHOLOGISTS’ - EXCHANGE. 
vain, I now find’it more frequently. At times 
it appears to be very active, while at other 
times it must be sought after, buried in the 
deep, soft mud. 
49.—Margaritana deltoidea, Lea. 
This small species was formerly abundant 
in our creeks, but is now nearly extinct. It is 
a smooth, triangular shell with a yellowish 
brown epidermis, and has the growth lines 
prominent and close. It has dull green rays, 
often interrupted by its numerous lines of 
growth. Some specimens are much inflated, 
while others are quite flat. The undulations 
on its beaks are coarse, but few in number. 
Cardinal teeth, double in both valves. 
50.—Margaritana marginata, Say, 
This remarkably fine shell is very rare here. 
I have found but a few specimens in Edwards 
and Pope Creeks, and but one specimen in the 
river. ‘This was taken near the mouth of the 
Iowa River, where it emptjes into the Missis- 
sippi at New Boston, and might have come 
from the former stream, This shell is plicate 
posteriorly, oblong in outline, and has very 
prominent undulations on its beaks, nearly 
This 
over the entire shell, interspersed with dots of 
green, yellow and sometimes, black. Epider- 
mis, yellowish brown. Nacre, white. 
Sub-Genus Anodonta, Brugiere. 
51.—Anodonta edentula, Say. 
Shell smooth, oval, with or without rays; 
rather solid, and extremely variable. ‘This fine 
species is found rather abundantly in this lo- 
cality. As it occurs here it is so extremely 
variable that itis almost impossible to describe 
it. There are at least three quite distinct va- 
rieties found here. One variety, which rarely 
occurs in Edwards Creek, very many collectors 
would scarcely regard as even a variety of 
edentula, When adult, it is quadrate in out- 
line, very much rounded at the extremities of 
the shell; inflated; umbonial slope rounded ; 
growth lines very close, striate or sulcate. Epi- 
dermis dark olive, often having green bands 
running parallel with growth lines. Rudimen- 
tary teeth very slight. Naere salmon color 
Lan 
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