GAMMARUS DUBIUS. 397 



I MPH1P0DA . GA MM A RIDES. 



NAT ATOM A. > '" 



DOUBTFUL SPECIES. 



We are under the necessity of introducing in the present situation two species 

 described as belonging to the present genus, by our late friend Dr. G. 

 Johnston, of Berwick-upon-Tweed, of which we have unfortunately been un- 

 able to meet with any specimen, either in the British Museum collection 

 or amongst the species which he forwarded to us some years since, for 

 the purposes of the present work. We therefore transcribe his descriptions 

 of them. 



GAMMARUS DUBIUS. 



Johnston, Zool. Journ. iii. p. 178. 



" Body between two and three lines long, smooth, 

 corneous; when dead becoming yellowish-brown; marked 

 across the back with a few red lines. Antennae rather 

 more than one-half the length of the body, slender, 

 nearly equal, armed with very short weak spines ; basilar 

 joint of the superior longer than the second or third, 

 which indeed might, with as great propriety, be reckoned 

 amongst the articulations of the last joint [flagellum] 

 as distinct joints ; basilar joint of the inferior shorter 

 than the succeeding. Eyes black, roundish, placed at 

 the base of the antennae. Arms with nearly equal 

 hands, monodactyle, oblong, and not much dilated, and 

 sparingly ciliated. They very much resemble those of 

 G. punctatus* in their form, but are rather smaller in pro- 

 portion to the body. Legs spiny, spines not collected 

 into fascicles, but distributed along the whole member ; 

 and both the short anterior and long posterior legs are 



* Amphithoe littoralis. Spence Bate. 



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