184 



increasing in length posteriorly. Opercular plates of the 2 anterior pairs of pleo- 

 poda with air-cavities, more rarely also those of 3rd or of all pairs. Copulative 

 organs of male nearly as in Porcellio. Uropoda rather produced, and of a similar 

 structure to that in Porcellio. 



Remarks. This genus established by Mr. Bndde-Lund, is nearly related 

 to Porcellio, though easily distinguishable from it by the smallness of the cephalic 

 lobes, the poor development of the side-plates of the mesosome, and the abruptly 

 contracted metasonie. The generic name refers to the fact, that the frontal edge of 

 the cephalon is nearly straight, not as in Porcellio produced in the middle. Mr. 

 Budde-Lund describes no less than 35 species of this genus, chiefly from the 

 southern part of Europe. Only a single species belongs to the fauna of Norway ; 

 it will be described below. 



Metoponorthus pruinosus (Brandt). 



(PI. LXXX, fig. 2.) 

 Porcellio pruinosus, Brandt, Consp. monogr. Crust. Isop. terrestr. p. 19, fig. 21. 



Syn : Porcellio truncatus, M. Edw. 

 maculicornis, Kocli. 



frontalis, Lereb. 



Porcellionides flavo-vittatus, Miers. 



Specific Characters. Body oblong, more than twice as long as it is broad, 

 dorsal face but slightly convex and nearly smooth, though, on a closer examina- 

 tion, exhibiting a very fine granulation. Cephalon transversely quadrangular, al- 

 most twice as broad as it is long, lateral lobes extremely small, frontal margin 

 straight. Side-plates of the 4 anterior segments of mesosome scarcely at all 

 projecting, those of the 3 posterior segments somewhat larger, with the posterior 

 corners obtusely acuminate. Metasonie not attaining 1 U of the length of the 

 body, and much narrower than the mesosome, epimeral plates of the 2 anterior 

 segments concealed, those of 3rd to 5th segments comparatively small, recurved ; 

 last segment nearly twice as broad at the base as it is long, subtriangular, tip 

 pointed. Antennula? with the last joint scarcely longer than the middle one. 

 Antennae very slender and elongated, exceeding half the length of the body, 

 flagellum somewhat shorter than the last peduncular joint, and having its prox- 

 imal articulation nearly twice as long as the distal one. Legs very slender, 

 minutely spinulose inside, propodal joint narrow, sublinear. Opercular plates of 

 only the 2 anterior pairs of pleopoda provided with air-cavities, and of somewhat 

 different shape in the two sexes. Uropoda with the outer ramus nearly twice as 

 long as the basal part, inner ramus extending scarcely to the middle of the 



