le of
nourishing themselves?"

_Thorax and Limbs._--The thorax is much compressed, and consists of six
segments, corresponding with the six pair of natatory legs; the anterior
segments are much plainer (even the first being distinctly separated by
a fold from the mouth), than the posterior segments, which is exactly
the reverse of what takes place in the mature Cirripede; in the latter,
the first segment is confounded with the part bearing the mouth. The
epimeral elements of the thorax are distinguishable; the sternal surface
is very narrow, and is covered with complicated folds and ridges. The
six pair of legs are all close, one behind the other, and all are alike
in having a haunch or pedicel of two segments, directed forwards,
bearing two arms or rami, each composed of two segments, the outer
ramus being a little longer than the inner one. On the lower segments
in both rami of all the limbs, there is a single spine. In all the
limbs, the obliquely truncated summit of the terminal segment of the
inner ramus bears three very long, beautifully plumose spines: in the
first pair, the summit of the outer ramus bears four, and in the five
succeeding pair, six similar spines. This difference, small as it is, is
interesting, as recalling the much greater difference between the first
and succeeding pairs, in the first and second stage of development. The
terminal segments of all the rami, bearing the long plumose spines, are
directed backwards. The limbs and thorax are well furnished with
striated muscles. The animal, according to Mr. King, swims with great
rapidity, back downwards. The limbs can be withdrawn within the
carapace.

_Abdomen and Caudal Appendages._--The abdomen is small, and its
structure might easily be overlooked without careful dissection of the
different parts: it consists of three segments; the first can be seen to
be distinct from the last thoracic segment, bearing the sixth pair of
limbs, only from the fold of the epimeral element, and from its
difference in shape; the second segment is very short, but quite
distinct; the third is four or five times as long as the second, and
bears at the end two little appendages, each consisting of two segments,
the lower one with a single spine, and the upper one with three, very
long, plumose spines, like those on the rami of the thoracic limbs. The
abdomen contains only the rectum and two delicate muscles running into
the two appendages, between the bases of whi