68 



longer than the other 3; inner expansion of proximal joint narrowly produced 

 at the end and extending about to the middle of the distal joint; marginal 

 setae only 4 in number. 



Colour not yet ascertained. 



Length of adult female 0.67 mm. 



Remarks. This is a very distinct and easily recognisable form, differ- 

 ing conspicuously from the other species both in the outward appearance and 

 in the structure of some of the appendages, though, according to the structure 

 of the antennae and of the 1st pair of legs, apparently referable to the 

 present genus. 



Occurrence. A solitary female specimen of this form was found in a 

 sample taken at Riser from a depth of about 50 fathoms. 



Gen. Hemimesochra, G. O. Sars, n. 



Generic Characters. Body sub-clavate in form, being conspicuously 

 tumefied in its anterior part and attenuated behind. Rostral plate small and 

 deflexed, not sharply defined behind. Segments of urosome coarsely spinulose 

 at the hind edge. Caudal rami of moderate size. Anterior antennae short and 

 stout, 5-articulate, with some of the setae on the proximal part coarsely pectinate, 

 last joint comparatively large, but not conically produced at the end and with 

 some of the setae ciliated. Posterior antennae with the outer ramus very small, 

 uniarticulate. Mandibles very strong, with the cutting edge imperfectly dentate; 

 palp well developed, but without any distinctly defined outer ramus. Maxillae 

 with the exopodal lobe obsolete. 1st pair of legs not prehensile, the inner 

 ramus being very short and only composed of 2 joints. The 3 succeeding 

 pairs of legs of a structure similar to that in Mesochra. Last pair of legs 

 likewise built on the same type as in that genus, the distal joint being very 

 small, not produced at the end. 



Remarks. This new genus is only founded on a single species, which 

 however exhibits certain peculiarities in the structural details forbiding its 

 reception into any of the known genera of the present family, though in some 

 respects it would seem to approch somewhat the genus Cletomesochra. 



