Pvn H,i I'UitlS

LEUA.
Genus II. LE'DA*, Schumacher. PL IV. f. 2.
153
Body transversely oval : mantle open in front, as well as on
the anterior side, and forming on the posterior side two cylin-
drical tubes of unequal length. Other characters as in Nucida .
Shell triangular- oval, or oblong : margin produced
on the
posterior side, and in some species slightly gaping or open :
lwn.uk lance-shaped : ligament, cartilage, and teeth as in Nucula,
except that the number of teeth on the anterior side is nearly
equal to that on the posterior side : pallial scar interrupted by
the tubes.
This genus is closely
tion and habits,
allied to Nucula in its distribu-
as well as in most of the characters exhi-
bited bv the animal and shell : but the mantle in Leda
forms two distinct tubes, and the shape of the shell is
oval or oblong, instead of triangular as in Nucula. The
teeth, also, in the present genus are set more obliquely,
and the disparity of number is less between those in the
front and those in the back row. It corresponds with
the genus Lembulus of Leach, quoted by Risso; and
according to Morch (' Gronlands Bloddyr ')
genus Nuculana, a name of prior
Schumacher.
it is Link's
date to that of
Yoldia is said to differ from Leda in
Holler's genus
the tubes being longer, and curved instead of straight,
in
the foot being larger and thicker, in the posterior edges
of the mantle being ciliated instead of plain, and in the
shell gaping at both ends, whereas that of Leda is closed
at the anterior end and truncate at the other ;
and the
posterior side has two or three blunt external ridges,
and an internal rib or epiphysis caused by the separation
of the tubes. But in L. minuta the posterior edges of
the mantle are ciliated, or fringed by short filaments,
and the shell of L.pygmaa, which is referred by northern
* A proper name in Greek mythology.
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