rotuberant than the upper
segments. Second cirrus; anterior ramus with six or seven basal segments
highly protuberant, and crowded with spines; posterior ramus with about
six segments, similarly characterised. Third cirrus with the anterior
ramus having six, and the posterior ramus five segments, also similarly
characterised.

_Caudal Appendages_ absent, there being only a slight swelling on each
side of the anus.

The _oesophagus_ runs parallel to the labrum, and enters obliquely the
summit of the stomach, which is destitute of caeca: the biliary envelope
is longitudinally plicated.

There are no _Filamentary Appendages_.

_Testes_ large, branched like a stag's horns, attached in a sheet to the
ventral surface of the stomach: the vesiculae seminales enter the
prosoma, and have their reflexed ends not very blunt. The _Penis_ is
rather narrow, with the terminal half plainly ringed, and bearing tufts
of fine bristles arranged in circles, one tuft below the other; on the
basal half there are only a few scattered minute bristles.

_Affinities._--In the downward growth of all the valves, in the presence
of a sub-rostrum, in the shape of the scuta, carina, and more especially
of the triangular latera, in the form of the peduncle, with its
irregularly-scattered calcified scales, in the shape of the animal's
body, in the structure both of the mandibles and maxillae, in the
arrangement of the spines, both on the anterior and posterior cirri,
_Scalpellum villosum_ most closely resembles, or rather is identical
with, Pollicipes. Had it not been for the formation of the valves
forming the capitulum, and from the presence of Complemental Males, I
should have placed this species alongside of _Pollicipes spinosus_ and
_sertus_. In not having caudal appendages, _S. villosum_ differs from
all the species of Scalpellum and Pollicipes; but this organ is variable
to an unusual degree in Pollicipes.

COMPLEMENTAL MALE. Pl. VI, fig. 4.

From the kindness of Professor Owen, Mr. Gray, and Mr. Cuming, I have
been enabled to examine six specimens of this species; and on two of
them I found Complemental males. They were attached in the same position
as in _S. Peronii_; namely, beneath the adductor muscle, in the fold
between the scuta, so as to be protected by the latter when closed. This
parasite is six-valved, and has a close general resemblance with that of
_S. Peronii_, but differs in very many points of detail. It is
represented o