ch the sinuous margin supports either a
continuous row or separate tufts of glands.

_Distribution._--The species abound over the arctic, temperate and
tropical parts of the Atlantic, Indian and Pacific Oceans, and are
always, or nearly always, attached to floating objects, dead or alive.
The same species have enormous ranges; in proof of which I may mention
that of the six known species, five are found nearly all over the world,
including the British coast; and the one not found on our shores, the
_L. australis_, apparently inhabits the whole circumference of the
southern ocean.

_General Remarks and Affinities._--The first five species form a most
natural genus; they are often sufficiently difficult to be
distinguished, owing to their great variability. The sixth species (_L.
fascicularis_) differs to a slight extent in many respects from the
other species, and has considerable claims to be generically separated,
as has been proposed by Mr. Gray, under the name of Dosima; but as it is
identical in structure in all the more essential parts, I have not
thought fit to separate it. As far as external characters go, some of
the species of Paecilasma have not stronger claims, than has _L.
fascicularis_, to be generically separated; and I at first retained them
altogether, but in drawing up this generic description, I found scarcely
a single observation applicable to both halves of the genus; hence I was
led to separate Lepas and Paecilasma. If I had retained these two genera
together, I should have had, also, to include the species of Dichelaspis
and Oxynaspis; and even Scalpellum would have been separable only by the
number of its valves; this would obviously have been highly
inconvenient. Although some of the species of Paecilasma so closely
resemble externally the species of Lepas, yet if we consider their
entire structure, we shall find that they are sufficiently distinct; as
indirect evidence of this, I may remark that Conchoderma (as defined in
this volume), includes two genera of most authors, and yet certainly
comes, if judged by its whole organisation, nearer to Lepas than does
Paecilasma.

1. LEPAS ANATIFERA. Tab. I. fig. 1. (_var._)

L. ANATIFERA. _Linnaeus._ Systema Naturae, 1767.

ANATIFA vel ANATIFERA vel PENTALASMIS laevis[24], plerumque
auctorum.

---- ENGONATA (!).[25] _Conrad._ Journal Acad. Nat. Sc.
Philadelphia, vol. vii, 1837, p. 262, Pl. xx, fig. 15.

---- DENTATA (va