eated between
the two segments, and is more in connection with the occludent than with
the basal segment; and this I cannot but think is an important
difference: in other respects, _P. fissa_ shows no more affinity to
Dichelaspis than do the other species of the genus. Finally, I may add
that Dichelaspis bears nearly the same relation to Paecilasma, as
Conchoderma does to Lepas.

1. DICHELASPIS WARWICKII. Pl. II, figs. 6, 6 _a_, _b_.

OCTOLASMIS WARWICKII. _J. E. Gray._ Annals of Philosophy, vol. x,
p. 100, 1825; Spicilegia Zoologica. t. vi, fig. 16, 1830.

_D. scutorum segmento basali duplo latiore quam segmentum occludens:
tergorum parte inferiore paulo latiore quam occludens scutorum
segmentum._

Scuta, with the basal segment twice as wide as the occludent segment;
terga, with the lower part slightly wider than the occludent segment of
the scuta.

Mandibles, generally with four teeth.

Off Borneo, attached to a crab (Belcher): China Sea. British
Museum.

_General Appearance._--Capitulum much compressed, elongated, with the
valves not very close together, the carina being separated by a rather
wide space from the scuta and terga. Valves variable in shape, very thin
and translucent, covered by thin membrane, which, over the whole
capitulum, is studded with minute blunt points.

_Scuta._--Segments without internal teeth or an internal basal rim; the
occludent segment long, narrow, pointed, not quite flat, sometimes
slightly wider in the upper part; about one third of its own length
longer than the basal segment; occludent margin slightly arched; basal
segment about twice as wide as the occludent segment, triangular,
slightly convex; in young specimens (Pl. II, fig. 6 _b_), the carinal
margin of the basal segment is protuberant, and the occludent margin
hollowed out; in old specimens the occludent margin of the basal segment
is straight, and the carinal margin much hollowed out. In very young
specimens the basal segment is very small compared to the occludent.

_Terga_, variable in shape; flat, lower part wider than the occludent
segment of the scuta; occludent margin double, forming a considerable
rectangular projection, as in the terga of Lepas; scutal margin deeply
excised at a point corresponding with the apex of the scuta, a flat
tooth or projection being thus formed; there is sometimes a second tooth
(fig. 6 _b_) a little above the basal point. The terga, in the first
variety, somewh