Pvn H,i I'UitlS

428 mactridjE.
that the laterals in the
separated : teeth as in Mactra, except
present genus are very small or rudimentary : pallial scar
having a deep sinus.
In comparing this genus with the last, we find that
the siphonal tubes in Lutraria are extremely long ;
that
the shell is large, oblong, very inequilateral, and gapes
and that the lateral teeth are much
widely at each end ;
less developed than in Mactra, and in one species altogether
wanting. The Lutraria burrow deeply in mud
near the shore.
Clark proposed to merge the present genus in My a ;
and there has been much controversy as to its systematic
position. It has certainly strong affinities both
with Mactra and My a. The last, however, has its man-
tle more closed, the tubes completely united, and a dif-
ferent kind of hinge-process.
1. Lutraria ellip'tica *, Lamarck.
L. elliptica, Lara. An. sans Vert. v. p. 468 ; F. &H. i. p. 370, pi. xii., and
(animal) pi.
H. f. 2.
Body white : mantle open only for one-third of its extent,
margined by rather distant fine white filaments : tubes tapering
; sheath between two and three times as long as the shell
is broad, white towards its base, variegated
in the middle with
zigzag purplish-brown blotches, which at the top become distinct
dots of a deeper hue the surface of the sheath is also
;
marked with two or three circular brown lines, an inch apart,
and it is covered with a transparent corrugated skin, wT kich
appears to be an extension of the epidermis
that clothes the
shell ; orifices of the tubes encircled by numerous white cirri
minutely spotted with dark purplish -brown or red ;
the cirri of
the alimentary tube are longer than the other set, and minutely
ciliated at their sides :
gills pale brown, not deep, the upper
pair rather smaller than the lower ; they are hung transversely,
and finely pectinated : palps of a paler colour, long, triangular,
pointed, of fine texture, and delicately striated: foot large,
thick, and extensile.
* Elliptical.