orium, are pale
blueish-grey, and the interspaces between them dark leaden-purple. The
cirri and trophi are generally dark purple or lead-colour.

_Filamentary Appendages._--These are attached to beneath the basal
articulation of first pair of cirri; they vary in the several species,
from one to five or six on each side, the lowest being always the
longest. Several of them are occupied by testes. In _L. pectinata_,
generally, not even one is developed. They are subject to great
variation in their proportional lengths, and in number, in the same
species. These organs have generally been considered to serve as
branchiae; I see no reason to believe that they are more especially
designed for this end, than is the general surface of the body.

_Mouth._--The labrum is moderately bullate, the longitudinal diameter of
this part equalling about one third, or half of that of the rest of the
mouth. The palpi are moderately developed. The mandibles (Pl. X, fig. 5)
have five teeth with the inferior point either broad, or very narrow and
tooth-like. The maxillae are step-formed (Pl. X, fig. 9); the first step
is sometimes indistinct and curved; and in _L. pectinata_, all the steps
vary much, and are more or less blended together. The outer maxillae
(like those at Pl. X, fig. 16), are internally clothed continuously with
spines. The olfactory orifices are not at all prominent.

_Cirri._--The first pair is placed near the second pair, and is of
considerable length; the second has the anterior ramus thicker than the
posterior ramus, and the segments brush-like; the segments (Pl. X, fig.
26) of the four posterior cirri bear from four to six pair of long
spines, with a row of small intermediate spines: in the posterior cirri
of _L. australis_ the lateral rim spines are much developed; and in
those of _L. fascicularis_, the usual pairs of large spines are lost in
a broad triangular brush, formed by the increase of the lateral
marginal, and intermediate spines.

_Caudal Appendages_ (Pl. X, fig. 18 _b_), very small, either blunt or
pointed, and quite destitute of spines.

The prosoma is well developed. The stomach is surrounded in the upper
part by a circle of large branching caeca. The generative system is
highly developed; the testes coating the whole of the stomach, entering
the filamentary appendages and the pedicels of the cirri; the two
ovigerous lamellae contain a vast number of ova; they are united to
rather large fraena, of whi