517 



Gen. 8. Msera, Leacli, 1813. 



Syn : Leptothoij, Stimpson. 

 » Megamaera, Sp. Bate. 



Body more or less slender, and quite smooth above, with comparatively 

 small coxal plates, tlie 4th pair of which is scarcely emarginated posteriorly. 

 Eyes present or subobsolete. Superior antennae longer than the inferior, and 

 provided with a well-developed accessory appendage. Mandibular palps slender 

 and densely setous, with the terminal joint the largest; basal lobe of 1st 

 pair of maxillse very narrow, and having only a few setae at the tip. Oral 

 parts normal otherwise. Gnathopoda more or less distinctly subcheliform, and 

 rather unequal, the posterior ones being the larger, and very strongly 

 developed in male. Pereiopoda slender, the 3 posterior pairs stronger than 

 the 2 anterior, and successively increasing in length, with the basal joint 

 more or less expanded. Last pair of uropoda projecting considerably beyond 

 the others, and having both rami well developed and uniarticulate, edged 

 with small spines. Telson comparatively small and bipartite. 



Bemarks. — This genus was established by Leach as early as in the 

 year 1813, to include the Gammarus grossimanus of Montagu. According to 

 Sp. Bate, the genus Lepfothoe of Stimpson is identical with the present 

 genus. Boeck combined the genus Meganioira of Sp. Bate with Mara, and 

 most subsequent authors have adopted this view. The genus is chiefly 

 distinguished by the slender, smooth body, the small size of the coxal plates, 

 the rather full development of the accessory appendage of the superior 

 antennae, and the structure of the last pair of uropoda, both rami of 

 which are well developed. It comprises several species both from the 

 northern and southern hemisphere. To the fauna of Norway belong only 

 2 species, to be described below. 



68 — Crustacea. 



(l^ 



