h traces of lines radiating from the umbones.
_Scuta_ with teeth on both sides, nearly equal; internal basal rim
rather wide, sometimes furrowed; basal margin considerably curved
inwards. _Terga_ rather wide; basal angle blunt; angle formed by the two
occludent margins blunt and rounded. _Carina_ (fig. 5 _a_) with the apex
blunt, flat; the middle part generally very broad; much constricted
above the fork, where it is internally deeply concave, and externally
carinated; fork twice as broad as the broadest upper part of the valve;
with the prongs flat, broad, thin, pointed, diverging at about an angle
of 75 deg., with the intermediate rim not at all reflexed; the fork
generally not deeply imbedded in the chitine membrane of the peduncle,
so as to be quite easily visible externally; sometimes there is an
internal, transverse, depressed line on the fork. In young specimens,
with the capitulum about a quarter of an inch long, the fork of the
carina is not developed, the lower slightly inflected portion consisting
simply of an oval plate, twice as wide as the upper part. Until I had
carefully examined a perfect series, showing the gradual changes in this
part, I did not doubt that the young specimens formed a distinct
species, and named it accordingly: the shortness of the penis first made
me perceive that the specimens were immature. At this early age, I may
add, the filamentary appendages were not developed. _Peduncle_ either
quite short, or as long as the capitulum, close under which it is
considerably constricted all round.

_Filamentary Appendages._--Two on each side; one long, tapering, placed
on the prosoma (in one specimen represented by a mere knob), and the
second shorter, situated on the posterior margin of the swelling beneath
the first cirrus.

_Mouth._--Maxillae, with three large spines at the upper angle, and with
the first step distinct, but narrow; mandibles with five teeth; in young
specimens the inferior point ends in a single spine; sides of the
supra-oral cavity very hairy; the membrane, forming the inner fold of
the labrum, yellow and thickened in the form of a spoon.

_Cirri._--In the posterior cirri there are, at the upper lateral edges
of the segments on _both_ sides, small spines; the segments in the first
cirrus, and in the broad anterior ramus of the second cirrus, are
hemispherically and considerably protuberant. Caudal appendages smooth.

_Size._--The largest specimen had a capitulum one inch