_85_ 



Epimeral plates of the 3 succeeding segments discontiguous at the tips. Last 

 segment of metasome very small, but wholly exposed. Urosome of moderate 

 length and much narrower than the anterior division, genital segment distinctly 

 divided in the middle. Caudal rami resembling those in Psamathe, but with the 

 apical' setae less elongated. Eye quite normal. Anterior antennae comparatively 

 slender, 9-articulate, not dilated in the middle. Posterior antennae with the outer 

 ramus more fully developed than in Psamathe. Mandibles with the palp rather 

 large, though of quite normal structure. Maxillae with the epipodal lobe well 

 developed and, as in Psamathe, carrying 2 large plumose setae. Maxillipeds com- 

 paratively more strongly built than in that genus, the anterior ones with 2 

 well-developed lateral lobes, the one close to the base, the other at the junction 

 with the slender unguiform terminal joint; the posterior ones terminating in a 

 strong claw accompanied by 3 or 4 slender setae. First pair of legs with the 

 inner ramus much as in Psamathe, outer ramus rather short and stout, with the 

 middle joint thickened, and armed on the lower face, close to the base, with a 

 strong, claw-like spine curving outwards, last joint very short, with the 4 apical 

 spines not pulvinular, being bent outwards and, like those in the genus Idya, 

 densely ciliated along the outer part of the anterior edge. Middle joint of inner 

 ramus in 2nd pair of legs with 2 natatory setae, that in the 2 succeeding pairs 

 with only a single such seta. Last pair of legs comparatively smaller than in 

 Psamathe, and more lamellar. 



Remarks. This genus was established in the year 1883 by Prof. Brady, 

 to include a species, M. idyoides Brady, found during the Challenger Expedition 

 at the Kerguelen Islands. As observed by that author, the genus is somewhat 

 intermediate between Psamathe (Scutellidium) and Idya, resembling in some par- 

 ticulars the former genus, in others the latter. Among the characters assigned to 

 this genus by Prof. Brady, is the presence of 2 widely-distant eyes; but this 

 statement must, I suppose, be due to a miscomprehension, the chitinous thicken- 

 ings at the insertion of the anterior antennae having in all probability been mis- 

 taken for eyes. The true visual organ, as in most other Harpacticoida, very soon 

 becomes inconspicuous in preserved specimens through the dissolving action of the 

 alcohol. There still remain, however, sufficient characters in support of this genus ; 

 and its validity is moreover now proved by the discovery in the northern ocean 

 of another form, which, though closely agreeing with the type in all essential 

 anatomical details, is yet evidently specifically distinct. 



