of an inch long;
only a few arrive at this size.

_Colours_, after having been kept in spirits,--sack and cirri,
especially first cirrus, clouded with pale purple; peduncle brownish;
valves appear blueish in specimens not long preserved, but in specimens
kept longer they become perfectly and delicately white.

_General Remarks._--Under the head of _L. anserifera_, I have made some
remarks on the diagnostic characters of this species. In the thinness of
the valves,--form of the carina, with the rim connecting the prongs
being not, or scarcely, reflexed,--and in the shortness and narrowness
of the peduncle, there is some approach to _L. australis_, and thence to
_L. fascicularis_. In the form of the maxillae,--in one specimen having
the mandible on one side bearing only four teeth,--and in the frequent
absence of filamentary appendages, there is some approach to the genus
_Paecilasma_; but there is no such approach in the characters derived
from the capitulum. We have seen that, as in so many other species of
this genus, most of the parts are variable, and this is the case to a
most unusual extent in the form of the maxillae. Dr. Leach has attached
eight specific names to the specimens preserved in the British Museum.

5. LEPAS AUSTRALIS. Pl. I, fig. 5.

_L. valvis glabris, tenuibus, fragilibus; scutorum dentibus umbonalibus
utrinque internis; carinae parte superiore lata, plana, supra furcam
valde constricta; furcae cruribus latis, planis, tenuibus, acuminatis,
intermedio margine non relexo._

Valves smooth, thin, brittle; scuta with internal umbonal teeth on both
sides. Carina with the upper part broad, flat; much constricted above
the fork, which has wide, flat, thin, pointed prongs, with the
intermediate rim not reflexed.

Filaments, two on each side.

Common on Laminariae in the whole Antarctic Ocean: Bass's
Straits, Van Diemen's Land: Bay of Islands, New Zealand, lat.
35 deg. S.: lat. 50 deg. S., 172 deg. W.: coast of Patagonia, lat.
45 deg. S.: attached to bottom of H. M. S. Beagle, lat. 50 deg. S.,
Patagonia: attached to a Nullipora, (I presume a drift piece,)
British Museum.

_General Appearance._--Capitulum rather obtuse and thick; valves thin,
brittle, approximate, either white and transparent, or dirty-brown and
opaque; or sometimes tinted internally with purple (perhaps the effects
of being preserved in spirits); surface plainly marked by lines of
growth, rarely marked wit