6 
purplish blue. Length 3-5, diameter and 
axis 3-10 of the breadth. 
In East Kentucky, very rare, 2 or 3 inch- 
es wide. Very singular shell, which I mis- 
took at first for a JV1 elaplera ; tubercle of the 
hinge hardly visible, lamellar tooth very 
long, close to the back, bifid at the end in 
the left valve. Type of a new Genus which 
may include other species when sought for 
in the south west. 
IV. Genus or tribe, Anodonta. 
112 Sp. Anodonla inflata. disc. 1822._ 
Shell thick, elliptical; somewhat atte- 
nuated behind, very much swelled; sum- 
mits wrinkled, subprominent, outside oli- 
vaceous, wrinkled, inside white iridescent. 
Length, 3-5, diameter 2-5, axis 3-10 of 
the breadth. 
Var. 1. Viridis. Green outside. 
Var. 2. Fuscata. Brown outside. 
Var. 3 . Zonalis. With green and brown 
zones. 
River Kentucky and Green, the largest 
and finest sp. of the West, reaching 5 and 
6 inches, hinge almost without any visible 
fold. 
113. Sp. Jlnodonla digonota. ( Lastena 
digonota, 1826.) Shell thin, oval swelled, 
back straight, obliqual, with two angles, 
one before and one behind, similar to 
small wings, sloping behind, with a flex- 
uose edge; outside laminated, pale, oliva- 
ceous, inside bluish white, iridescent. 
Length 5-8, diameter 3-8, axis at 1-4 of 
the breadth. 
From Lake Erie, two inches, hinge in- 
side. with a flexuose fold, separated from 
the straight back. Perhaps a peculiar S. 
G. Flexiplis . 
I have besides, another doubtful Jlnodon - 
to; Jl. rufa , probably a var. of A. ohiensis, 
sp. 58. 
V. Genus or tribe, CYCLAS. 
I have no new sp. of Cyclas; but I am 
enabled to present a beautiful new genus 
of this tribe, which forms the passage be- 
tween Unio and Cyclas. I call it Diplas - 
ma, meaning double lamellar teeth. The 
specimen before me, was not collected by 
myself; it belongs to the cabinet of shells 
of Mr. Hembel, of this city, who has 
had the goodness to lend it to me. It is 
labelled Unio , and is supposed to come 
from the river Tennessee, which I am in- 
clined to doubt, because I have in my ca- 
binet, a specimen nearly alike, from the 
river Ganges, collected by Dr. Burroughs, 
and because the G. Diplasma appears to be 
Asiatic. I therefore suspect that this spe- 
cies of Mr. Hembel, is also from Hindos- 
tan, and shall therefore include it in the 
the following 
APPENDIX, 
On eight Asiatic bivalve jluviatile shells . 
These shells were all collected in the 
rivers of Hindostan, by Dr. Burroughs of 
this city. They appear very different from 
our North American shells, forming even 
often peculiar genera. They are 3 sp. of 
Diplasma , I sp Loncosilla , 2 sp. Lampsilis , 
and I Obliquaria , 
9. N. G. DIPLASMA. 
Shell inequilateral and transversal, hinge 
with two lamellar teeth, nearly confluent, 
united into a curve, not serrulate, more or 
less unequal, bilamellar anteriorly in the 
right valve, bilamellar posteriorly in the 
left valve. 
Certainly a distinct Genus, more like 
Cyclas and Hina , in the hinge than Unio , 
although so labelled by Dr. Burroughs, and 
our conchologists, by the external form 
merely. I suspect that many Asiatic Unios 
belong to it. I shall describe 3 of them, 
besides our doubtful American species. 
114 Sp. Diplasma marginala . Shell thin, 
elliptical, swelled, back horizontal, sloping 
and truncate obliquely behind; outside ve- 
ry smooth, shining brown, anterior and in- 
terior margin yellowish, inside pale incar- 
nate. Length one half, diameter 1-3, axis 
3-10 of the breadth. 
From the river Tennessee, as stated to 
Mr. Hembel, but so near the next, that the 
fact appears doubtful to me; perhaps the 
locality has been erroneously stated or la- 
belled in Mr. Lea’s cabinet, from whence 
the shell is said to have come, and it may 
be also a shell from Hindostan. Lamellar 
tooth properly curved, the anterior pretty 
long. Size of the shell over two inches. 
115 Sp. Diplasma similis. Shell very 
thin, elliptical, not swelled, back horizon- 
tal, truncate obliquely behind, hardly slop- 
ing, outside smooth, dark olivaceous, with 
a pale margin, inside bluish incarnate. 
Length 7-15, diameter 4-15, axis 15 of the 
breadth. 
From the river Ganges, so similar to the 
last as almost to appear the same, yet thin- 
ner, flatter, and teeth somewhat different, 
forming almost an angle rather than a 
curved arch, anterior tooth shorter, ob- 
lique, the posterior perfectly horizontal. 
Length nearly two inches. 
116 Sp. Diplasma vitrea. Shell very thin 
and brittle, almost transparent, oval swell- 
ed, broader behind, with a slope outside, 
very smooth, greenish, or fulvescent, inside 
whitish, teeth subequal. Length 2-3, dia- 
meter 2-5, axis 2-5 of the breadth. 
From the river Jellinghy in Bengal. 
Small, hardly over one inch, fine delicate 
shell. 
117 Sp. Diplasma striata. Shell thick, 
suboval, swelled, behind sloping subtruncate 
and transversally striated, outside olivaceous 
greenish, smooth below, but longitudinally 
striated above; strias in a zigzag form in the 
middle, inside silvery white, teeth subequal, 
much curved. Length 2-3, diameter 2-5, 
axis 5-12 of the breadth . 
Also from the river Jellinghy. Small, 
hardly one inch. This and the last agree in 
many points, and might form a peculiar sub- 
