Pvn H,i I'UitlS

268 CARDIID^.
loped in the tertiaries, while from the present seas not
less than 200 species have been obtained."
It is much more difficult to reconcile the synonymy
of our native species than to distinguish them. As Loveii
has justly remarked, " Cardia europsea misere confusa."
I will endeavour not to increase this perplexity, with-
out disregarding, however, the established rules of pri-
ority and general usage.
The meaning of the generic name (heart-shaped)
will appear when the united valves are viewed in profile.
The genus Cerastes was formed by Poli for the animal.
A. Shell more or less globular ; ribs strong, and covered with
spines, tubercles,
or vaulted scales.
This section may be further subdivided into
a. Round. 1. C. aculeatum. 2. C. echinatum. 3. C. tu-
berculatum. 4. C. papillosum.
b. Triangular. 5. C. eociguum. 6. C. fasciatum. 7. C.
nodosum. 8. C. edule.
c. Longitudinally oval. 9. C. minimum.
1. Cardium aculea'tum * 9 Linne.
C. aculeatum, Linn. Syst. Nat. p. 1122 F. & H. ii. ; p. 4, pi. xxxiii. f. 1.
Body of a vermilion colour : foot long and awl-shaped.
Shell very gibbous, with a somewhat oblique outline, thin
for its size, opaque and rather : glossy sculpture, 20-22 strong
compressed ribs, which are a little broader than the furrows
between them ; each rib is divided in the middle by a ridge of
spines, which bend towards the posterior side, being longer and
double on that part and tubercular on the anterior side ; the
furrows are transversely striated, or in aged specimens are
marked with flexuous wrinkles ; in younger shells there are a
few irregular longitudinal lines, giving the furrows an appear-
* Thorny.