502^ 



the sea. Subsequently I have also met with it in the Christianiafjord, at 

 Moss, where it occurred in quite shallow water among algse. 



Distribution. British Isles (Leach), Kattegat (Copenhagen Museum). 



11. Gammarus Duebeni, Lilljeborg. 



(PI. 177, fig. 1). 

 Gammarus Duebeni, Lilljeborg, 0fvers. af Kgl. Svenska Vet. Acad. Forhandl. 1851, p. 22. 



Syn. : Gammarus campylops, Norman (not Leach), 

 locusta, var. C, Hoek. 



Form of body about as in G. locusta. Cephalon having the lateral 



corners, as in G marinus, transversely truncated, and denned below by a rather 



deep sinus. Coxal plates smaller than in G. locusta, and more nearly similar 



to those in G. marinus. Last pair of epimeral plates of metasome but 



slightly produced at the lateral corners. Segments of urosome scarcely 



produced dorsally, and each provided with 2 dorsal spines, and on either side, 



with a group of 3 spines, being moreover clothed with numerous rather long 



hairs. Eyes not very large, and distinctly reniform, as in G. locusta. Superior 



antennae not quite half as long as the body, 1st joint of the peduncle scarcely 



attaining the length of the other 2 combined, flagellum about twice the length 



of the peduncle, accessory appendage not nearly half as long as the latter, 



and composed of about 6 articulations. Inferior antennae considerably shorter 



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



peduncle, and in male provided with distinct calceolee. Gnathopoda in female 



somewhat resembling those in G. locusta, though the propodos of the posterior 



ones appears less narrow; those in male not nearly so strongly developed 



as in that species, and also less unequal in size. The 3 posterior pairs of 



pereiopoda comparatively less slender than in the 2 preceding species, and 



having their outer part clothed with fascicles of rather long bristles; basal 



joint of antepenultimate pair rounded at the infero-posteal corner. Last pair 



of uropoda with the inner ramus but little exceeding half the length of the 



outer, both rami densely setiferous. Telson rather broad, each half with 4 



apical spines, 1 subapical (sometimes wanting on one of the sides), and from 2 to 4 



lateral spines near the base, and being besides clothed with long diverging 



hairs. Body generally of a very dark colour, with 3 pink patches on each 



side of the metasome, as in G. locusta. Length of adult male 15 mm., that 



of female considerably less. 



