dd that I opened another quite young specimen, from
Adelaide, not counted with the above, and it was without a male. The
males in the five specimens were attached low down, at the rostral end,
almost in a horizontal position, stretching across the bottom of the
sack; one of them, however, was placed considerably on one side. One
individual which I measured, was 16/100ths of an inch in length, and
5/100ths in width in the widest part, namely, about half down the
peduncle. I may state, for the sake of comparison, that the
hermaphrodite to which this individual was attached, was, including the
peduncle and capitulum, one inch in length, that is, six times as long
as the male, and one fifth of an inch in width, that is, four times as
wide. The above measurements show that the male of this species is
rather more than twice as large as that of _I. Cumingii_. In consequence
of this greater size, I dissected, with the utmost care, the one
specimen which was excellently preserved in spirits, and found every
part, with a few exceptions, so exactly the same as in the male of _I.
Cumingii_, only larger and more conspicuous, that it will be sufficient
to indicate the few points of difference.

The most conspicuous difference is, that the oblique fold separating the
thorax and peduncle is more plainly developed, projecting at the point
corresponding to _h_ in fig. 1, Pl. V, 8/1000ths of an inch; in the
middle the fold is notched; it can be traced more easily than in _I.
Cumingii_, running beneath and parallel to the basal edge of the mouth,
to the ventral margin of the body. In the mouth there is hardly any
difference; the maxillae, however, have two notches even plainer than in
the hermaphrodite _I. quadrivalvis_, or than in the male _I. Cumingii_,
but the depth of such notches is always a variable character; there are
also more spines on the edge in the male of the present species, than in
_I. Cumingii_. Both mandibles and maxillae in the male _I. quadrivalvis_,
are larger than in the male _I. Cumingii_, to a greater degree than the
larger proportional size of the body in the former will account for; and
this, likewise, is the case with these same organs in the hermaphrodite
_I. quadrivalvis_ compared with the female _I. Cumingii_. The tubular
olfactory orifices are situated in the same peculiar position as in the
hermaphrodite, and as in both sexes of _I. Cumingii_: they are 1/500th
of an inch in diameter, and about as thick as one