394 GAMMARIM. 



Gervais, who first clearly pointed out the distinction 

 between it and De Geer's smooth-tailed species, for 

 which he retained the name of G. pulex. As already 

 stated, we fear that M. Milne Edwards has fallen 

 into some confusion in treating upon these fresh-water 

 species. He placed one, to which he applied the name 

 of G. fluviatilis, in his section without teeth on the 

 anterior, but with small spines on the posterior segments 

 of the tail ; but he refers his species not only to De Geer, 

 whose figures perfectly agree with this sectional charac- 

 ter, but also to Rosel, Geoffroy (whose pi. xxi. fig. 6, 

 is copied from Rosel), and to Gervais, all of whom as 

 certainly intend a tooth-backed species. To add to the 

 confusion, M. Milne Edwards expressly says that the 

 penultimate joint of the peduncle of the superior an- 

 tennae reaches the tip of the peduncle of the lower ones ; 

 and adds, under G. marinus, that the sixth pair of caudal 

 appendages scarcely extend beyond the extremity of the 

 preceding pair of the same organs. The other fresh- 

 water species of M. Milne Edwards is still more un- 

 intelligible ; this he names G. pulex, placing it in the 

 section which has no teeth on the first three segments, 

 and no spines on the posterior segments of the tail, and 

 giving as its references, Geoffroy, Linnaeus (?), Fabricius, 

 and Latreille, all doubtful, as well as Montagu, Desma- 

 rest, Zenker, and Gervais, whose species has spines on 

 the terminal segments of the tail. 



i - We have stated above that Linnaeus employed the 

 name Pulex aquaticus in the Fauna Suecica exclusively for 

 a marine or littoral species, but in his Systema Natures 

 he says : " Habitat ad maris littora, etiam in fontibus et 

 fossis," thus confounding a sea and a fresh-water species 

 together; but we have not the slightest means of knowing 

 to what fresh-water species he alluded. Fabricius, on 

 the other hand, although he quotes De Geer's figures 



