, and nearly
half as long as the whole of the sixth cirrus; they have a small tuft of
long thin spines at their ends, and a few in pairs, or single, along
their whole length; at first I thought that they were multi-articulate,
but after careful examination I can perceive no distinct articulations;
I have seen no other instance of so long an appendage without
articulations.

_Diagnosis._--This species differs from _D. Grayii_ in all the valves
being shorter, so that their points only just cross each other; but
this, I conceive, is an unimportant character. In the scuta, the basal
segment is here narrower, but the point of junction of the two segments
wider than in that species; in the terga, the edge of the axe is smooth
instead of being crenated, and the handle and the point behind are of a
rather different shape; in the carina the imbedded basal disc has not
shoulders and small teeth, as in _D. Grayii_. Notwithstanding these
differences, I should not be much surprised if the present form were to
turn out to be a mere variety.

4. DICHELASPIS LOWEI. Pl. II, fig. 8.

_D. scutorum segmento basali angustiore quam occludens segmentum,
longitudine fere 4/5: tergorum parte inferiori duplo latiore quam
occludens scutorum segmentum._

Scuta with the basal segment narrower than the occludent segment, and
about four-fifths as long as it. Terga with the lower part twice as wide
as the occludent segment of the scuta.

Mandibles with four teeth; segments of the three posterior cirri with
eight pair of main spines.

_Hab._--Madeira; attached to a rare Brachyourous Crab,
discovered by the Rev R. T. Lowe. Very rare.

_General Appearance._--Capitulum much compressed, sub-triangular, formed
of very thin membrane; valves imperfectly calcified, and thin.

_Scuta_ formed of two narrow plates placed at about an angle of 50 deg.
to each other, and united at the umbo by a non-calcified flexible portion.
The primordial valve is situated at this point, but chiefly on the
occludent segment. The occludent segment is about twice as wide and
about one fifth longer than the basal segment, which latter is rather
sharply pointed at its end. The occludent segment is slightly arched, a
little narrowed in on the occludent margin close to the umbo; its upper
end is broad and blunt; it runs throughout close to the edge of the
orifice of the sack, and its longer axis is in the same line with that
of the terga. Close to the umbones, on the