dirty white, partly invested by yellow
membrane, furnished with a few minute yellow horny spines. Pedicels of
the first four cirri, caudal appendages, penis, the two posterior
thoracic segments, the segments of the cirri, and the trophi, clouded,
banded, or spotted, with blackish purple.

_Affinities._--This species, in the characters derived from the valves,
comes perhaps nearest to _L. Rhodiopus_; in the characters derived from
the animal's body, it is nearest to _L. dorsalis_.

4. LITHOTRYA RHODIOPUS. Pl. VIII, fig. 4.

BRISNAEUS RHODIOPUS. _J. E. Gray._ Annals of Philosoph., vol. x,
(new series,) 1825.

---- ---- _J. E. Gray._ Spicilegia Zoolog., Tab. xvi, fig. 17,
1830.

_L. scutis terga ample obtegentibus: carinae crista interna tenui, in
parte superiore posita: lateribus, superficie interna symmetrice et late
ovata, carinae latitudinis plus quam tertiam partem aequantibus: tergorum
basali apice tenui, et angulo carinali producto: rostro et pedunculo
ignotis._

Scuta largely overlapping the terga. Carina with a slight central
internal ridge in the upper part. Latera with their internal surfaces
symmetrically and broadly oval, more than one third of the width of the
carina. Terga with the basal points narrow, and the carinal angle
produced. Rostrum and peduncle unknown.

Mandibles, with four times as many pectinations between the first and
second main teeth, as between the second and third; distance greater
between the tips of the first and second teeth, than between the tip of
the second tooth and the inferior angle. Maxillae widely notched, with
the inferior part forming two obscure prominences.

Hab. unknown. Imbedded in a massive coral. Brit. Mus.

The specimens are in a rather bad condition, and have been
disarticulated. They are of rather small size; the rostrum and peduncle
are lost, and animal's body much injured.

Valves white, thin, translucent; teeth on the projecting rims small,
narrow, standing further apart than their own width. The upper layers
have undergone but little disintegration or scaling off, and
consequently the carina and terga project freely. The valves, where not
rubbed, are covered by bright yellow membrane, which is thickly clothed
with rows of spines; these are small on the exterior surfaces, but are
very large and hooked in certain parts, as near the tergal margins of
the scuta, and on the carinal margins of the terga, and especially on
the inner