r 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. Kroeyii_, 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
chelae impinge through their whole length; outer margin of the hand
furnished with 3 or 4 small spines.

_Hab._ Trawling-ground, Plymouth, common; Moray Frith, Scotland.

This species unites _G. Andrewsii_ with _G. nexa_, and, I think, has
often been mistaken for the young of the latter; but _G. nexa_, so far
as my experience goes, is a species peculiar to the north of England,
whereas _G. dispersa_, I anticipate, will be found to be the most
universally dispersed, in deep water, of any of the species known. It
can always be detected from _G. nexa_ by the form of the hand and the
manner in which the fingers impinge: in _G. nexa_ the hand is broad
towards the extremity, and the fingers meet only at the apex; in _G.
dispersa_ the hand gradually narrows to the apex, and the fingers meet
each other through their whole length, the inner margin of the finger
being finely serrated, the thumb not.

It also may be distinguished from _G. Andrewsii_ by the breadth of the
hands, which are narrow and round in _G. Andrewsii_, and moderately
broad and flat in _G. dispersa_.

By an examination of the texture of the integument