Journal of the Proceedings of the Linnean Society - Vol. 3 | Page 2

as exist in the order
Brachyura, whilst the external antennæ have the long and slender
flagella proper to the Macrura. The scale, however, commonly
appended to the external antennæ in the latter order is wanting, a
circumstance which exhibits a relation to the Brachyura.
An examination of the legs shows that the coxæ are fused with the
thorax, as in the Brachyura, and not articulated with it as in the Macrura,
whilst, on the other hand, the posterior division and caudal termination
approach the Macrural type more nearly than that of the Brachyura, the
animal thus assuming a character intermediate between the two orders.
But in the description of the several species of the genus Galathea, a

peculiar difficulty appears to arise, originating in the affinity which
they bear to each other. So close, in fact, is the approximation, that the
descriptions of the best writers will scarcely avail for the distinction of
the individual species without the assistance of figures. This arises
from the fact that the general characters, upon which the descriptions
are based, vary, in this genus, only in their comparative degrees of
development.
In the three species recognized in Professor Bell's work on the British
Crustacea, it will be found that each species retains the same characters
in greater or less degree.
Galathea strigosa is peculiar for the spinous character of the carapace
and cheliform legs. Every spine, however, is repeated in both the other
species, only less developed. We find the rostrum furnished with four
lateral teeth on each side, a character which also exists in each of the
other species; and although close observation may detect a slightly
different arrangement in the relative position of these teeth, the
differences are not of sufficient importance to enable a naturalist thence
to derive a specific distinction, unless the peculiarity is seconded by
some more unqualified character less liable to be affected by any
peculiarity of condition.
In order to arrive at more certain results in the identification of species,
we think that the microscopic examination of the surface of the
integument will be found peculiarly useful.
This mode of examination of species may also be applied to a
considerable extent throughout the Crustacea generally with great
advantage; and if found valuable in recent, there can be no doubt that it
will prove of far greater importance in extinct forms, where parts on
which the identification of species visually rests are lost, and fragments
only of the animal obtainable.
It should be borne in mind that, as the structure in question undergoes
modifications more or less considerable in different parts of the animal,
it will always be advisable to compare the corresponding parts with
each other.

Applying this test to the known species of Galathea, we perceive that
the structure of the integument upon the arms, independent of the
marginal spines, exhibits a squamiform appearance, but that the scales,
which characterise the structure, possess features peculiar to each
species.
In Galathea strigosa the scales are convex, distant from each other,
smooth at the edge, and fringed with long hairs. In G. squamifera they
are convex, closely placed, scalloped at the edge, and without hairs. In
G. nexa the scales are obsolete, tufts of hair representing the supposed
edges. In G. depressa, n. sp., the scales are broad, less convex than in G.
strigosa and G. squamifera, smooth, closely set, and fringed with short
hairs. In G. Andrewsii they are small, distant, very convex, tipped with
red, and slightly furnished with hair.
As another instance of the practical application of the microscopical
examination of the surface, I would refer to two species of Amphipoda,
classed by Leach under the name of Gammarus Locusta, from his
inability to assign them any separate specific characters. In the structure
of their integuments, however, these two forms will be found to exhibit
widely different microscopical appearances.
Again, there exists in the same group three or four species, the
description of any one of which would apply to either of the others; and
it is probable they would never have been ranked as separate species
had not their habitats been geographically distant. Thus Gammarus
Olivii, M.-Ed., G. affinis, M.-E., G. Kröyii, Rathke, and G. gracilis, R.,
can only be specifically determined by a microscopic examination of
the integument.
The same may be said of other Amphipoda, such as Urothoe inostratus,
Dana, from South America, which so nearly resembles in form the U.
elegans of the British shores.
GALATHEA DISPERSA, mihi.
G. rostro brevi, dentibus 4 utrinque ornato, 2 anterioribus minoribus;
pedibus anterioribus elongatis, sparse spiosus; chelarum digitis

parallelis.
Galathea with short rostrum, armed on each side with 4 teeth, the two
posterior being less important than the two anterior. The fingers of the
chelæ impinge through their whole length; outer margin of the hand
furnished with