44 



ORCHESTinm 



formed of two equal lobes. The second scale-like joint 

 of tlie last three pairs of legs is oval. The caudal ap- 

 pendages are short and strong. 



The animal generally is longer and more compressed 

 than A. Nilssonii. The dorsal ridge is slightly elevated 

 into a carina, which is most conspicuous towards the pos- 

 terior limit of each segment. This gives to the animal, 

 when viewed laterally, an imbricated appearance, from 

 which circumstance we have taken the name, and by 

 which the species can easily be determined from any other 

 known British form. 



A. imbricatus appears to be rather local. The first 

 specimens that we received were from Penzance, where 

 they were taken by Mr. George Barlee, between tide- 

 marks. In company with Professor Kinahan we have 

 found them on the Breakwater at Plymouth, where they 

 live in small pools left in the holes worn by the wash of 

 the sea in the surface of that stupendous work. We found 

 many individuals, and they appeared to be the only species 

 of Amphipod that existed there. The colour was a bluish- 

 grey, but a few were almost black. 



The following vignette is a sketch of the Western end 

 of the Breakwater by Mr. Philip Mitchell, of Plymouth. 



