95 
rufous lines very much dilated, but they still preserve the zigzag 
form. 
Venus pr^parca. — Shell subovate, with numerous, elevated, 
subacute, parallel, concentric lines, which subside into mere 
wrinkles near the suture of the ligature slope, interstitial spaces 
plain ; ligament slope flattened, margined by an acute line ; ante- 
rior margin with an obsolete, longitudinal, very obtuse undulation, 
which gives the tip of this margin a slightly truncated appearance; 
areola cordate, elevated at the suture ; within white or yellowish ; 
inferior and posterior margins within crenulated, the crenulse ex- 
tending along the edge of the areola to the beak ; in advance of 
the anterior termination of the ligament groove of the left valve, 
is another distinct groove which receives the edge of the corres- 
ponding margin of the other valve. 
Width two inches and one-fourth. Inhabits the coast of the 
United States. Cabinet of the Academy and Philadelphia Mu- 
seum. 
This species bears considerable resemblance to F. casina, but 
that shell is regularly arquated on the anterior margin in Maton 
and Rackett’s figure (v. Trans. Lin. Soc. Lond. 8, pi. 2, fig. 1.) It 
also approaches F. rigida^ but is distinct by its cordate areola, &c. 
Venus elevata. — Shell subcordate, longitudinally sulcated, 
sulci equal, numerous, dense, on the anterior submargin sparse ; 
concentric elevated, remote, lamellar bands ; anterior margin sub- 
angulated at tip ; within, margin crenated, crenge obsolete on the 
anterior margin, and near the hinge on the posterior margin. 
Length four-fifths of an inch. Breadth nine-tenths of an inch. 
Inhabits the Southern coast. Cabinet of the Academy. 
I obtained but a single bleached valve of this species. It cer- 
tainly approaches very near to F. cancellata, but it is distinguish- 
ed by being much less obtuse before, and by having the longitu- 
dinal strige more numerous. The concentric lamellar bands were 
eleven in number on this specimen. 
Venus inequalis. — Shell subcordate, longitudinally sulcated, 
lines numerous, obsolete on the anterior margin, behind the middle 
bifid and alternating with smaller single ones ; concentric, distant, 
lamellar bands, but little more elevated than the longitudinal lines ; 
anterior margin subangulated ; within, margin crenate, crenge obso- 
