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specimen, is unquestionably identical with Kroyer's species. It is one of our 

 largest Harpacticoida, and differs sconsiderably in its outward appearance from the 

 other Tbalestridse, a fact which may no doubt be accounted for by its very dif- 

 ferent habits. 



Occurrence. Only a very limited number of specimens of this peculiar 

 form, all of them females, have hitherto come under my notice. They were taken 

 partly off the Finmark coast, partly off the west coast of Norway, and in every 

 instance in the open sea at a considerable distance from the shore and near the 

 surface, together with other pelagic animals. 



Distribution. British Isles (Brady), coast of Spitsbergen (Scott). 



Gen. 31. RhyilChOthaleStriS, G. 0. Sars, n. 



Generic Characters. Body more or less robust, with the 2 chief divisions 

 rather sharply marked off from each other. Cephalic segment large and deep, 

 with the rostrum very prominent and very mobile. Urosome comparatively 

 short, with the anterior segments more or less expanded laterally. Caudal rami 

 short, but with the apical setae rather elongated. Eye well developed. Anterior 

 antennas of usual structure, 9-articulate. Posterior antennas with the proximal 

 part distinctly divided in the middle, outer ramus composed, of 3 well-defined 

 joints. Oral parts normal and rather fully developed. 1st. pair of legs of a 

 structure similar to that in Thalestris. Natatory legs with the spines of the outer 

 ramus coarsely denticulate, middle joint of inner ramus in all the pairs carrying 

 2 seta3 inside. Last pair of legs of moderate size, with the distal joint more 

 prominent than the proximal one. 



Remarks. This new genus is chiefly characterised by the unusually sharp 

 demarcation of the 2 divisions of the body, and more particularly by the strong 

 development of the rostrum, a. character which has given rise to the generic name 

 here proposed. In the structure of the several appendages also some well-marked 

 differences from the preceding genera are found to exist, especially as regards 

 the posterior antennse and the natatory legs. Two well-defined Norwegian species 

 are referable to this genus, both having been previously described as species of 

 the genus Thalestris. 



