170 C. Spence Bate on the Pencidea. 
of small hook-like processes that Sars has called “ eineinnuli ;” 
this membrane (which I propose to call ‘‘ petasma,” from its 
curtain-like character), when at rest, lies folded up in a manner 
peculiar to each separate species. 
The second pair of pleopoda, like all the others posterior to 
it, is two-branched, besides which there is in the male a rudi- 
mentary branch attached to it that varies much in different 
species, which variations, without being very important, are 
yet valuable addenda for the determination of closely approxi- 
mating forms. The other pleopoda gradually decrease in length 
posteriorly. 
In the female the vulve are situated at the extremity 
of open projections on the third (that is, the posterior of 
the chelate) pair of pereiopoda; and, in most instances, in the 
family Peneide the organs face each other and almost touch 
in the median line. Posterior to these a ventral plate of 
varying form and appearance, according to species, lies be- 
tween the last two pairs of legs; connected with this, varying 
also in form with species, a large mass of brown membranous 
material is attached: in some species large and fan-like in shape, 
in others it is an irregular oval disk; but what relation it has 
to the true history of the animal, observation has yet to de- 
termine. 
The first pair of pleopoda, as in the male, is single-branched, 
and the petasma is reduced to a rudimentary process; and the 
second pair of pleopoda does not carry a small additional 
branch. Add to this the singular fact that among all the 
specimens in the ‘ Challenger’ collection, as well as those in 
the British Museum and the typical collection of the Jardin 
des Plantes, there is not a single specimen in which the female 
has either ova or the remains of ovisacs attached to the hairs 
of the pleopoda—a circumstance which, compared with the 
great frequency with which ova in all stages are found in 
nearly every genus of the class besides, is highly suggestive, 
either that the Penzidea are viviparous, or that the young 
like those of some fish, are hatched floating in the sea. 
What form the Brephalus may take is yet to be determined : 
it may be what Fritz Miiller has pronounced it to be; but 
whether it be a Nauplius, a Zoéa, or a Megalopa must be 
decided by future observation. 
After comparing the specimens in my possession with the 
descriptions in the works of the best-known carcinologists, 
such as Milne-Edwards, De Haan, Dana, Stimpson, Heller, 
&c., I examined the collection in the British Museum, under 
the care of Mr. Miers, who has recently drawn up a “ synoptic 
table of the species of Peneus,” which was published in 
