OF THE INTEGUMENT OF CRUSTACEA. 3 



parts on which the identification of species usually 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 corre- 

 sponding 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 characterize the structure, possess features 

 peculiar to each species. 



In Qalathea 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. squa- 

 mifera^ 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 micro- 

 scopical examination of the surface, I would refer to two species 

 of Amphipoda, classed by Leach under the name of Gammartis 

 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 

 GammartLS Olivii, M.-Ed., G. qffinis, M.-E., G. Kroyii, Eathke, and 

 G. gracilis, H., can only be specifically determined by a micro- 

 scopic examination of the integument. 



The same may be said of other Amphipoda, such as TTrothoe 

 inostratus, Dana, from South America, which so nearly resembles 

 in form the IT. elegans of the British shores. 



Galathea dispersa, mihi. 



G. rostro brevi, dentibus 4 utrinque ornato, 2 anterioribus minoribus ; 

 pedibus anterioribus elongatis, sparse spinosis ; chelarum digitis 

 parallelis. 



1* 



