n both genera, has an
unusual oblong form, like a mule's hoof; there is also an affinity
between the two genera in the size and form of the ova, in the prominent
orifices of the olfactory cavities, and in the peduncle not being naked;
though, in these two latter respects, in the structure of the cirri, and
in the multiarticulate caudal appendages, there is an equal affinity to
Pollicipes and Lithotrya. I have already shown that Alepas is likewise
related to Ibla.

1. IBLA CUMINGII. Pl. IV, fig. 8.

_I. (foem.) valvarum marginibus lateralibus, et superficie interiore,
caeruleis: pedunculi spinis plerumque annulis caeruleo-fuscis._

Fem.--Valves coloured, along the lateral margins and on the upper
interior surface, blue: spines on the peduncle, generally ringed with
blueish-brown.

Caudal appendages barely exceeding in length the pedicels of the sixth
cirrus: rami of the first cirrus unequal in length by about two
segments.

Male,--with scarcely a vestige of a capitulum: maxillae with fewer spines
than in the female.

_Hab._--Philippine Archipelago, Island of Guimavas; invariably
attached to the peduncle of _Pollicipes mitella_, in groups of
two or three together; Mus. Cuming. Tavoy, British Burmah
Empire; Mus. A. Gould of Boston.

FEMALE.

The capitulum is formed of four valves, but is hardly distinct from the
peduncle. The latter includes, in its wide upper part, the animal's
body. The valves, namely, a pair of scuta and terga, are composed of an
extremely hard, horny substance, or properly chitine, and do not contain
any calcareous matter; they are extremely flat or thin, and both pairs
project freely, like curved horns, to a considerable height above the
sack enclosing the body: the terga project about twice as much as the
scuta, and their flat apices generally diverge a little. The tips of the
valves are frequently broken off; their surfaces are plainly marked or
ribbed by the layers of growth, which are wide apart. The bases of the
valves externally are hidden by the long spines of the peduncle.

_Scuta._--These are shorter and broader than the terga; their internal
(Pl. IV, fig. 8 _b'_) growing or corium-covered surfaces are slightly
concave, triangular, with the basal margin longer than the other margins
and slightly excised in the middle: there is no depression for the
strong adductor muscle: the internal surface of the free horn-like
portion, has a small central fold (formed by an