ly strong and long, beneath which, there is a deep notch
with a single strong spine, and with the whole inferior part square and
much upraised, so as to stand on a level almost with the tips of the
great upper spines.

_Cirri_ in a miserable state of preservation; first cirrus short, second
cirrus with rami unequal, and I suspect the anterior one the longest;
some of the other cirri also have unequal rami. The segments of the
posterior cirri are not protuberant, they have on their anterior faces a
single transverse row of bristles: in the upper segments, some of the
spines in each dorsal tuft (which is much spread out), are _much_
thicker, though rather shorter than those on the anterior face. This
peculiar structure is common to all five posterior cirri.

_Caudal Appendages._--I can only say that they are spinose on their
summits.

_Affinities._--This species is allied to _P. eburnea_ in the rudimentary
condition of its terga; in the disc-shaped basal end of its carina; and
in the presence in some specimens, of a fissure-like line on the scuta
parallel to their occludent margins. Its affinity, however, is closer to
_P. fissa_, as is more especially shown by the remarkable arrangement of
the spines on the five posterior cirri.

4. PAECILASMA FISSA. Pl. II, Fig. 4.

_P. valvis 7; scuto utroque e duobus juxtapositis segmentis formato;
segmento altero intus dentato: tergis brevibus, ter aut quater carina
latioribus: carinae termino basali in discum parvum angustum infossum
producto._

Valves 7; each scutum being formed of two closely approximate segments;
of which one is internally toothed: terga short, three or four times as
wide as the carina: carina with the basal end produced into a small,
narrow, imbedded disc.

Spines on the segments of the posterior cirri arranged in single
transverse rows.

Philippine Archipelago; Island of Bohol; parasitic on a spinose
crab, found under a stone at low water; single specimen, in
Mus., Cuming.

_General Appearance._--Capitulum gibbous, broadly oval, nearly a quarter
of an inch long. Valves white, smooth, moderately thick, marked by the
lines of growth. The occludent segments of the scuta, and nearly the
whole of the terga, and the whole of the carina, enveloped in
lemon-yellow membrane, tinged with orange, but the specimen had long
been kept dry.

_Scuta_ formed of two, apparently always separate, segments, closely
united, so that externally their separat