Pvn H,i I'UitlS

222 KELLIID^.
diately fixes itself, when placed in a basin of sea- water,
by its threadlike byssus. The foot protruded, but not
in action, occupies a central position : it is usually pushed
through
the slit at the base of the tube on the anterior
side when the animal wishes to move forwards, and, fixing
itself by a kind of suction, rapidly draws the shell after
it ; and it can also execute a similar movement backwards,
but more slowly.
out forming a byssal attachment ;
The animal never remains long with-
but when inclined to
move, it seems to have no difficulty in slipping its cable,
which is always discarded and left in situ. The surface
of the shell is sometimes coated with confervoid spores,
giving it a greenish appearance. My largest specimens
are from Shetland.
Walker first noticed and figured this species in his
account of minute and rare shells from Sandwich; but
his description was excessively meagre, and no specific
name was added. It is in all probability the Amphi-
desma nucleoid of Lamarck, Erycina violacea of Scacchi,
Cycladina Adansonii of Cantraine, Erycina Fontenayi of
Mittre, and Bornia seminulum of Philippi. Stimpson
remarks that the Kellia rubra of Gould is not our spe-
form and much smaller
cies, having a more compressed
beaks. He therefore gave the name of planulata to the
North-American species. Gould's figure seems to re-
present
Montacuta bidentata.
Genus TV. KEL'LIA*, Turton. PI. V. f. 3.
Body globular : mantle folded on the anterior side (being the
shorter and smaller end of the shell), so as to form a bag-shaped
incurrent tube, and folded on the opposite side into an excur-
rent tube, which is more prominent but shorter :
gills two, sym-
* Named after the Rev. J. M. O'Kelly of Dublin, a conchological asso-
ciate of Dr. Turton.