113 

 Gen. 3. Pleurogonium, G. 0. Sara. 



Syn: Pleuracantha , G. 0. Sars (olim). 



Generic- Characters. — Body short, depressed, with the 4 anterior segments 

 of mesosome more or less strongly dilated, the 3 posterior ones much smaller, 

 and having the lateral parts obliquely recurved. Cephalon comparatively small, 

 deeply sunk within the 1st segment of mesosome, and without any frontal lobes 

 or ocular processes. Caudal segment narrowly cordate or pyriform, constricted 

 at the base, tip more or less produced. Eyes wholly absent. Antennas differing 

 but little in size, and of a structure similar to that in Paramunna. Mandibles 

 without palps, cutting part narrowly produced, molar expansion slender, lappet- 

 shaped. 1st pair of legs short and strong, subcheliform ; the others slender, in- 

 creasing in length posteriorly. Female operculum lanceolate, male, of a simi- 

 lar structure to that in Paramunna. Uropoda very small, biramous, placed 

 somewhat dorsally, and at a considerable distance from the tip of the caudal 

 segment. 



PeniarJcs. — This genus was established by the present author in the year 

 1863; but the name Pleuracantha, proposed at that time, having been already 

 appropriated, he changed it subsequently to Pleurogonium. The genus is nearly allied 

 to Paramunna, but differs very markedly in the shape of the cephalon and caudal seg- 

 ment, as also in the absolute want of eyes and of mandibular palps. In addition 

 to the 3 Norwegian species described below, Mr. Beddard has recorded 3 other 

 species from the Challenger Expedition as P. albidum, serratum and minutum. 



l. Pleurogonium rubieundum, G. 0. Sars. 



(PI. XLVII, fig. 2.) 



Pleuracantha rubicunda, G. 0. Sars, Om en anomal Gruppe af Isopoder (Chr. Vitl. Selsk. Forh. 



1863), p. 16. 



Specific Characters. — Anterior division of body in female nearly circular 

 in outline, the breadth almost equalling the length. Cephalon sub-pentagonal in 

 form, with the front obtusely produced, and the sides obtusangular. Lateral parts 

 of the 4 anterior segments of mesosome subangular, and each carrying in the 

 middle a very conspicuous rod-like spine, all the spines pointing in different 

 directions, so as to exhibit a radiating arrangement. The 3 posterior segments 

 of mesosome very small, with the lateral parts extended obliquely behind, and 

 each terminating in a knob-like projection. Caudal segment rather narrow, con- 

 siderably constricted at the base, side-edges evenly curved, and fringed with short 



15 — Crustacea. 



