ELMINIUS KINGII. _J. E. Gray._ Zoological Miscellany, p. 13, 1831.
---- LEACHII. _King_ and _Broderip_. Zoological Journal, vol. 5,
1832-1834, p. 334, and appendix to King and Fitzroy's Voyages.
---- ---- _G. B. Sowerby._ Genera of Recent and Fossil Shells,
Plate.
_Shell smooth, gray or dirty white: radii broad, smooth-edged: scutum
without an adductor ridge; tergum with the spur distinct from the
basi-scutal angle: scutum and tergum sometimes calcified together._
_Hab._--Tierra del Fuego, Falkland Islands, Chiloe. Attached to tidal
rocks and sometimes to floating timber; Mus. Brit., Darwin, &c.
_General Appearance._--Shell fragile, either steeply conical with a
large orifice, or sub-cylindrical; surface smooth, grayish or white,
with large portions covered by pale brown epidermis. Radii broad with
their summits oblique, smooth, slightly arched, exhibiting a large
surface of the alæ. The alæ usually have their summits much less
oblique than those of the radii; the portion added during diametric
growth is of a dead white colour. The growth ridges on the scuta
are very little prominent, and are crossed by a very obscure band
of blueish-gray. The largest specimen which I have seen was .8 in
basal diameter, and the longest cylindrical variety .55 of an inch in
height.
The _Scuta_ are remarkable for not having any adductor ridge or
crests for the depressor muscles; the articular ridge is prominent,
but it is short, not extending down half the valve. I have mentioned
under the genus, that in many specimens at the Falkland Islands the
scuta and terga were calcified together.
The _Terga_ are rather small: the basal margin on the carinal side
of the spur is always hollowed out, but to a very variable degree,
as may be seen in the three figures (6 _c_-6 _e_); this margin is
generally dentated with one or two little points; and an inner lamina
of shell sometimes depends beneath the outer lamina, to which the
opercular membrane is attached, as may be seen in the figure (6 _d_)
of the external surface of the valve. The crests for the depressor
muscles are well developed. The tergal margin is broadly inflected,
and the articular ridge prominent, making the articular furrow deep.
The spur is rather narrow, and is either (6 _d_, 6 _e_) bluntly or
sharply pointed. The basal margin on the scutal side of the spur, is
hollowed out, but to a variable depth.
_Structure of the Parietes and Radii._--The parietes are thin; at
their internal basal edges they are finely striated in longitudinal
lines. The radii are solid, with quite smooth edges; they are
generally covered by the epidermis. The sutural edges of the alæ are
likewise smooth, these are added to largely during the diametric
growth; and their summits, as already stated, are much less oblique
than the summits of the radii. The internal surface of the shell
is smooth, and is tinted pale dull purple. The lower edge of the
sheath can hardly be said to be free. The carinal margins of the
compartments project a little inwards.
_Mouth_: the labrum is deeply notched, and supports five little teeth
on each side; the palpi are thickly clothed with spines on their
inner sides; the mandibles have five or only four teeth: the maxillæ
are notched, and the outer maxillæ bilobed.
_Cirri_: the first pair has one ramus nearly twice as long as the
other. The three posterior cirri are elongated, and each segment
supports five or six pairs of long spines, with a few minute
intermediate bristles.