172 
Unio cuneatuSj Va7\ Barnes. (^Note to Hildrethb s essay. ^ 
Unio planulatuSy Lea. Trans. American Philos. Soc. N. S., 
vol. 3, pi. 9, p. 13. 
Desc. Shell transversely oblongovate, thick ; surface yellowish 
brown^ with several rather broad radii^ which are often interrupted^ 
by the larger lines of growth^ into spots ; disks and umbo com- 
pressed ; beaks simple or not undulated ; not elevated ; cavity of 
the hinge membranes or lunule oval^ acute ; ligament not elevated* 
within white^ somewhat grooved obtusely ; cardinal plate very 
thick^ with a considerable flattened space between the cardinal 
and lateral teeth ; cardinal teeth rather small^ direct ; lateral teeth 
very short, oblique, and very thick ; anterior smaller muscular 
impression immediately anterior to the tips of the lateral teeth. 
Ohs. A striking similarity exists between this shell and the 
cuneatus and gihhosus of Barnes, the latter of which, however, is 
somewhat more slender, the cardinal teeth larger, the lateral teeth 
longer, the beaks undulated. 
In a note on Dr. Hildreth’s description of pTiaseolus^ Barnes 
says it is a “ white variety of cuneatus and it must be confessed 
that a considerable resemblance exists between some of their varie- 
ties. But the latter species differs in the much less dilated car- 
dinal plate ; in having the anterior smaller muscular impression, 
situated immediately beneath the tip of the lamelliform teeth ; in 
having the anterior lunule much more depressed, with slightly 
elevated lines crossing the wrinkles. 
The young of a corresponding age, accurately resembles, in its 
outline, Barnes’ figure of his mucronatuSj but his description of 
mucronatus agrees better with cuneatus than with any other species, 
certainly much better than with gihhosus^ inasmuch as it is stated 
to be purplish on the margin, and whitish in the centre,” whereas 
the latter is more commonly whitish on the margin than in the 
centre, and the anterior lunule long, distinct, with a marginal 
furrow,” of mucronatus, agrees with cuneatus, but not at all with 
gihhosus. 
This species is found in plenty in the Wabash, and is probably 
also an inhabitant of most of the larger tributaries of the Ohio. 
.The branchial oviducts, when inflated with eggs, exhibit a series 
of tubes, which, when dried, appear granulated under the micro- 
scope ; these tubes are dirty yellowish, with a few blackish spots 
