nes. On the
antero-lateral faces of the pedicels of the second, third, and fourth
pairs of cirri, there is an elongated white swelling or shield.
Moreover, on the posterior thoracic segments, there are similar
white-coloured swellings, with the membrane more plainly marked with
scales than in other parts. The spines on the first three pairs of
cirri are coarsely serrated.

_Caudal Appendages_ (Pl. X, fig. 23), with numerous tapering segments,
almost equalling one and a half times the length of the pedicel of the
sixth cirrus. Each segment is elongated and somewhat constricted in the
middle, with its upper edge (fig. 24) crowned with short spines; in a
full-sized specimen there were seventeen segments.

2. LITHOTRYA CAUTA. Pl. VIII, fig. 3.

_L. scutis terga ample obtegentibus: carina intus concava: rostro
squamarum subjacentium latitudinem vix aequante: lateribus, squamas
subjacentes sesquitertio superantibus; superficie interna late
elliptica: pedunculi squamis superioribus verticillum secundum paene
quadruplo superantibus._

Scuta largely overlapping the terga: carina internally concave: rostrum
hardly as wide as one of the subjacent scales: latera with their
internal surfaces broadly elliptical, as long as two and a half of the
subjacent scales: upper scales of the peduncle nearly four times as
large as those in the second whorl.

Mandibles with an equal number of pectinations between the first,
second, and third main teeth: maxillae notched, edge nearly straight:
posterior rami of the second and third cirri, with their basal segments
not paved with bristles: caudal appendages slightly exceeding in length
the pedicels of the sixth cirrus.

New South Wales, Australia, imbedded in a Conia, (unique
specimen,) Mus. Stutchbury.

Valves thin, white, translucent; upper layers of growth well preserved,
excepting on the terga. A large portion of the carina projected freely.
The teeth on the projecting margins of the growth-layers are broad,
blunt, and often stand rather distant from each other.

_Scuta_ (Pl. VIII, fig. 3 _a_), triangular, internally concave with no
distinct pit for the adductor muscle. The scuta largely overlap the
terga.

_Terga_ (fig. 3 _b_) approaching to rhomboidal; basal angle rectangular,
almost central, and consequently the exterior longitudinal ridge, which
is rounded, is likewise nearly central.

_Carina_, internally concave, with no trace of a central internal ridge
in the up