Pvn H,i I'UitlS

venus. 327
ment of the genus beyond the separation of Tapes and
Lucinopsis, I will indicate the divisions in the same way
as I have grouped other genera. Those belonging to
the genus Dosinia of Scopoli (Arthemis of Poli), Cytherea
of Lamarck, and Timoclea of Leach are the
most remarkable; but the gradation from one to the
other, as well as from each to the typical form,
slight to warrant such a multiplication
is too
of names for
a few objects which, it must be confessed, are closely
related. In the species first alluded to, the siphon al
tubes are united for their entire length, which is not
the case in most other species. But nearly the same
diversity
has been observed between individuals of the
same species (V. gaUina), and it exists also between
Tapes pullastra and T. decussatus, which clearly are
congeneric. The shell of V. exoleta (the type of Dosinia
or Artemis) differs little in shape from that of Circe or
of some varieties of V. fasciata. The type of Cytherea
(V. Chione) has an extra tooth and a nearly smooth
surface ; but in all other particulars it is a true Venus ;
and I agree with Mr. Clark that we have something
more to do than to " ring the changes on trivial points."
Callista was the name given by Poli to the animal of
Venus, Tapes,
and Mactra.
A. Mantle-tubes united throughout. Shell nearly orbicular,
concentrically imbricated; inside margin plain.
1. Venus exole'ta*, Linne.
V. exoleta, Linn. Syst. Nat. p. 1134. Artemis exoleta, F. & H. i. p. 428.
pi. xxiii. f. 3, 4.
Body suborbicular, pale yellowish-white : mantle having its
edges fringed with close-set white cilia, which are most distinct
* Worn awav.