fine bristles; the inferior part of the edge is step-like, and much
upraised.

_Outer Maxillae_, with the inner edge deeply notched, and the bristles
arranged in two quite distinct tufts; the bristles on the outer surface
are long. Olfactory orifices, thin, tubular, and projecting.

_Cirri._--The first pair is placed far from the second; the three
posterior pair are long and straight, with their segments much
elongated, not protuberant, bearing four or five pair of long spines,
with little intermediate tufts of minute spines, and with the minutest
spines on the lateral upper edges. Dorsal tufts with one spine extremely
long, equalling a segment and a half in length; the others very short.
Spines all serrated. First cirrus not very short; rami nearly equal,
with the four terminal segments of both tapering; all the basal segments
much thicker, and thickly covered with bristles. Second cirrus (as well
as the third in a less degree), with the anterior ramus thicker than the
posterior ramus, and with all the lower segments in both rami thickly
clothed with three or four longitudinal rows of spines.

_Caudal Appendages_, spinose, uni-articulate; but the specimen was
injured, and I could not exactly make out their shape: I believe it was
oval, and thickly fringed with fine spines.

_Penis_, very small, almost rudimentary, narrow, and hairy, scarcely
exceeding in length the pedicel of the sixth cirrus.

COMPLEMENTAL MALE. Pl. VI, fig. 5.

Before describing the parasite of the present species, which departs
entirely from the character of the males of the three preceding species,
it is proper to state that I consider it to be a Complemental Male
simply from analogy, as will hereafter be more fully shown at the end of
the genus. Had a specimen of the parasite been brought to me without any
information, I should have concluded that it was an immature individual
of a new genus of pedunculated Cirripedes, remarkable from the
rudimentary condition of the valves, and exhibiting, in one important
character, namely, in the form of the larval prehensile antennae, an
alliance to Scalpellum. Had I been then told that three individuals in a
group, had been found attached to _S. rostratum_, not outside the
valves, but to the integument, in a central line, between the labrum and
the adductor scutorum muscle, in such a position that when the
Scalpellum closed its valves, these parasites were enclosed within the
capitulum, my surprise wo