THE + CONCHOLOGIS’ 
rs’ - EXCHANGE. 
Gulf of Mexico and West Indies. They live 
buried in mud and sand more than a foot below 
the surface, and beyond low water mark, and 
are not easily obtained, as they cannot be 
reached by the dredge. I found one specimen 
alive at Apporang, but single valves are common 
on all our shores, and often both valves united, 
without the animal, and with the epidermis 
half worn off. 
. To be 
Continued. 
BRIEF NOTES ON THE LAND AND 
FRESH-WATER SHELLS OF MER- 
CER CO., ILL. 
BY WILLIAM A. MARSH. 
(Continued. ) 
54.—Anodonta plana, Lea. 
Shell smooth, oval, inflated and solid. Beaks 
large, but somewhat depressed and rounded 
over the umbones. Epidermis from light olive 
to dark brown, and sometimes greenish. When 
young this shell is often beautifully rayed, al- 
though it is sometimes found without rays. 
Undulations on beaks few and small. Nacre 
varying from dull salmon to white. Anterior 
portions of shell slight'y rounded. ‘This shell 
is found only in our creeks where it attains a 
large size, and is now very rare. It differs 
from grandis in being much more inflated, very 
much more solid and attains a larger size, and 
when adult it is very much more cylindrical 
I have collected specimens 7 inches wide, 4 
inches long, and 2% inches thick. It seems 
to prefer muddy bottoms, where there is little 
or no current in the stream. I often find it in 
mill ponds and sometimes in the mill races. 
As found here it is as more easily separated 
from grandis than is A, corpulenta. 
ta, Cooper. 
oF 
Shell smooth, oval, very much inflated, undu- 
lations prominent, beaks massive, very much 
56.—Anodonta suborbiculata, 
swollen and incurved, having a copper colored 
summit. The epidermis varies from dark brown 
and olive to dark green. Found both with 
and without rays. Nacre copper colored. This 
fine species is found very abundantly in the 
river sloughs and the small lakes of the Bay 
Island. It never ventures into the river, pre- 
ferring soft, muddy bottoms and _ still water 
where there is no current. It often attains a 
large size; the largest covfelenta in my collec- 
tion being 4% inches long, 7 inches wide, and 
3 inches deep. ‘The largest evandis I have, 
was received from Mr. A. A. Hinkley, of Wash- 
ington Co., Illinois, collected by him in South- 
ern Illinois. It measures 4 inches in length, 
6% inches in width, and 2 inches in depth. 
Corpulenta is extremely variable, as individuals 
are often found quadrate, with the hinge line 
perfectly straight, very tumid and almost round 
before and behind. I have one remarkably 
fine specimen which measures only 4 inches in 
width and measures the same otherwise as the 
one just described. Although corpulenta is 
generally very much inflated, specimens are 
often found that are much depressed. 
Say. 
This very fine shell is found only in the 
sloughs and small lakes of the Bay Island. 
Fifteen years ago it was quite common, and 30 or 
40 specimens might have been collected in a sin- 
ele day ; but itis now extremely rare and the col- 
lector may think himself well off if he secures 
2 or 3 specimens in a whole season. Dead 
shells are often found along the margin of Swan 
Lake, but live ones are seldom obtained. For 
two or three years I have been offering the 
fishermen 25 cents a piece for every live speci- 
men, but as yet they have failed to find it. 
This, our most attractive Anodonta, has a geo- 
graphical distribution from Indiaha to Kansas, 
and is probably not common in any particular 
locality. But five localities for this. shell are 
reported in Illinois, 
Shell suborbicular and somewhat depressed. 
Beaks not prominent, with small undulations 
and few in number. Epidermis pale green, 
light yellow and light brown in different speci- 
mens. Growth lines not prominent; the whole 
surface of the shell covered with beautiful mi- 
