164 



Remarks. This form was recorded as early as the year 1864 by Norman 

 as a species of Cythere, and was described the following year by the present 

 author under the name of Cytheropsis tenuitesta. It is easily distinguished 

 from the preceding species, both as to the shape and sculpturing of the shell, 

 and to the structure of the appendages, and I am indeed perplexed to see, 

 that Brady and Norman in one of their more recent papers have suggested 

 these 2 forms to be only varieties of a single species. 



Occurrence. I have only seen a few specimens of this species, taken, 

 many years ago, in the upper part of the Christiania Fjord. Norman records 

 it also from Finmark. 



Distribution. British Isles, Bay of St. Lawrence, Franz Josef Land, Medi- 

 terranean. 



Fossil. Scotland. 



Gen. 35, Krithe, Brady & Robertson, 1874. 



Syn: Ilyobates, G. O. Sars. 



Generic Characters. Shell thin and pellucid, though rather firm, with the 

 surface smooth and polished; inner duplicatures of valves very broad in front, 

 marginal zone crossed by scattered, somewhat irregular pore-channels am 

 surrounded in front by a thin hyaline border. Hinge imperfectly developec 

 Eyes absent. Anterior antennae with the basal segments very coarse am 

 expanded, terminal part rather movably articulated with the basal one, and 

 very short and compact, armed with slender upwards-curving spines. Posterior 

 antennae with 3 claws on the terminal joint, flagellum well developed in both 

 sexes. Mandibles with 2 of the cutting teeths much larger than the others, 

 vibratory plate of the palp small, with 2 apical setae and a rudiment of a 

 lateral one. Maxillae about as in Cytheridea. Legs comparatively short, 

 terminal part of the 2 anterior pairs only composed of 2 joints, by the co< 

 lescence of the 2 outer ones; left 2nd leg in male very powerful, subprehensih 

 Caudal rami and genital lobes about as in Cytheridea. 



Remarks. This is a rather anomalous genus, and its reference to th< 

 present subfamily appears indeed somewhat questionable. Yet, as I do n< 

 find a better place for classifying this genus, and as I am unwilling to estal 

 lish a new subfamily only founded on a single genus, I have preferred to 

 include it provisionably in the subfamily Cytherideince, with which it agree 

 at least in one essential character, viz., the partial transformation of the legs 

 in the male sex. The genus was established in the year*1865 by the present 



