useum, from an unknown locality, both had
shields on the segments of the cirri, but only one had the large plate
on the prosoma. I may here mention that in one specimen, in which the
calcified plates were most developed, and which was nearly ready to
moult, there were, within the filamentary appendages on the prosoma,
small irregular balls of calcareous matter, appearing to me as if
calcareous matter had been morbidly excreted, and not like a provision
for the future.

_Range._--This species, in the present state of our knowledge, seems to
range further than any other of the genus, extending from Upper
California, (lat. 32 deg. to 35 deg. N.,) across the Pacific, to at least
32 deg. S., perhaps much farther south, for it was collected during the
Antarctic expedition, and 32 deg. was the highest latitude traversed by
that expedition.

_Affinities._--This species is closely related to _P. cornucopia_ and
_P. elegans_, but differs rather more from them, than these two do from
each other. In the capitulum the chief distinctive characters are--the
more perfect graduation in size, and the greater number, (taking
equal-sized specimens,) of the whorls of latera--the darker colours--the
central part of the basal margin of the carina in this species, being
considerably excised--the peculiar form of the basal margin of the
scuta--and lastly, the scutal margin of the terga being more hollowed
out. In the animal's body, the most obvious distinctive character is the
uniarticulate caudal appendage. This species agrees with _P. elegans_,
in the presence of the singular elbowed teeth, on some of the spines in
the first three pairs of cirri.

4. POLLICIPES MITELLA. Pl. VII, fig. 3.

LEPAS MITELLA. _Linn._ Systema Naturae, 1767.

POLLICIPES MITELLA. _G. B. Sowerby._ Genera of Shells, fig. 2.

POLYLEPAS MITELLA. _De Blainville._ Dict. Sc. Nat. (1824) Plate,
fig. 5.

CAPITULUM MITELLA. _J. E. Gray._ Annals of Philosoph., new series,
vol. x, 1825.

_P. capitulo valvarum unico sub-rostro verticillo instructo: laterum
pari superiore (introrsum spectanti) inferiorum magnitudinem ter aut
quater superante: lateribus inferioribus utrinque obtegentibus:
pedunculi squarmarum verticillis densis, symmetrice dispositis._

Capitulum with only one whorl of valves under the rostrum: the upper
pair of latera, viewed internally, are three or four times as large as
the lower latera, which overlap each other laterally: sca