504 



twice the lengtli of the peduncle, accessory appendage comparatively small, 

 and only composed of 4 articulations. Inferior antennae, as usual, considerably 

 shorter than the superior, flagellum about the length of the last 2 joints 

 of the peduncle combined, and provided in male with distinct calceolaj. 

 G-nathopoda in female comparatively small, and slightly unequal, the pos- 

 terior ones being considerably more slender than the anterior, with the 

 propodos very narrow, oblong, and nearly transversely truncated at the tip ; 

 those in male somewhat more strongly built, though not very unequal in 

 size, propodos of the anterior ones obpyriform, of the posterior, oblong 

 quadrangular. Pereiopoda comparatively slender and elongated, with the 

 outer joints clothed with fascicles of slender spines, basal joint of antepen- 

 ultimate pair rounded at the infero-posteal corner. Last pair of iiropoda 

 rather elongated, inner ramus about the length of the 1st joint of the outer, 

 and having only a single spine on the inner edge near the base; both rami 

 edged Avith long, partly ciliated setae. Telson comparatively small, each 

 half with only a single lateral spine and 2 apical ones. Colour more or less 

 dark brownish green. Length of adult male attaining 20 mm, that of female, 

 as usual, considerably less. 



Remarls. — There cannot be any doubt that the <.<SquiUe pouce» of 

 De Geer is this species. Whether Linne's Cancer pulex is the species here 

 treated of, or the G. locusfa, appears somewhat doubtful; but as both a 

 Cancer locusfa and a G. pulex are qiioted, it is most reasonable to believe that 

 these names refer to different species. The G flnviatilis of M. Edwards is 

 unquestionably the present species, and very different from the Sqvilla 

 fliiriafilis of floessel, which was named by Gervais G. Roesselii. In his 

 Catalogue of Amphipoda in the British Museum, Sp. Bate applies the name 

 G. pulex to the latter species, whereas the form here treated of is termed 

 G. fluviatilis. The inverted application of these 2 names is undoubtedly the 

 most correct. I at first thought the Norwegian form to be a distinct species, 

 as I found it only in greater lakes, not, as stated, with G. pulex, in rivers, 

 and on this account I at first recorded it as G. lactistris n. sp., subsequently as 

 G. neglectus Lilljeborg M. S. I now, however, believe this assumption to be 

 erroneous. Boeck, it is true, I'ecords G. pulex and G. neglectus as two distinct 

 species; but his type specimen of G. pidex does not differ in any respect 

 from the form which I had named G. neglectus. From the other 4 species 

 here described, this is at once distinguished by its small eyes, the comparatively 

 short accessory appendage of the superior antennae, and the unusually slender 

 and elongated pereiopoda. 



Occurrence. — The present species is a true fresh-water form, and 

 cannot properly be derived from any of the marine species as a so-called 



