280 GAMMARID^. 



seen than in the present genus as compared with Leu- 

 cothoe and Stimpsonia. In these genera the first pair 

 forms a most effective organ of prehension, the pre- 

 hensile power being, however, developed in different 

 joints of the limb. In Leucothoe and Stimpsonia it is the 

 carpus which is remarkably produced, but in Aora the 

 metacarpus becomes the analogue of the carpus of the 

 two former genera. 



At first sight it might seem that this genus should be 

 incorporated in that of Microdeutopus, but the fact of 

 exotic species possessing the characters here laid down 

 sufficiently warrants their retention as a separate genus. 



We think it not improbable that further observation 

 may induce the removal of the closely-associated genera 

 in which the peculiar tubular kind of tail-scale is found, 

 from the position in which we have placed them among 

 the Gammarides, to one nearer the genus Nania among the 

 Podocerides. The difference in the relative strength of 

 the two pairs of antennas will also afford some clue to 

 the propriety of such a change of position. 



