240 



and prolonged, basal lamella of 1st pair very small and provided with 4 delicate 

 setae, last pair with the 1st joint of the terminal part shorter than the other 

 2 combined. 



Male a little smaller than female and having the shell comparatively 

 narrower, with the dorsal margin slightly concav. Copulative appendages very 

 small, with the basal part only slightly dilated, terminal part well defined, in 

 the form of an oval deflexed lamella somewhat angularly produced behind. 



Colour of shell whitish, transparent. 



Length of adult female scarcely exceeding 0.55 mm. 



Remarks. The above-described form is easily recognisable from any of 

 our other Cytherids, both as to the general appearance of the shell and to 

 the somewhat anomalous structure of the antennae. It is the type of the 

 present genus. 



Occurrence. 1 first found this form in the upper part of the Oslo Fjord 

 at a depth of about 40 fathoms, soft clayish bottom, and have subsequently 

 met with it also in some other places on the Norwegian coast up to the 

 Trondhjem Fjord in similar depths. In spite of its small size, it is easily 

 detected in any sample taken up by the dredge, owing to a particularity which 

 it shares with some other Cytherids, viz., that the animals, when coming in 

 contact with the air, remain floating on the surface of the water. 



Distribution. Britisch Isles, Fosse de Cap Breton, Bay of Biscay, Mediter- 

 ranean, Kerguelen. 



Fossil. Scotland, Ireland. 



Gen. 47. Macrocythere, G. O. Sars, n. 



Generic Characters. Shell elongate, compressed, sharply pointed behind, 

 without any lateral expansions. Hinge imperfectly developed. Eyes absent. 

 Anterior antennae with the segments of the basal part considerably dilated, 

 terminal part comparatively shorter than in By thocy there, but, as in that genus, 

 composed of 4 joints only slightly differing in length. Posterior antennae 

 without any dividing suture of the penultimate joint. Mandibles and maxillae 

 of a structure nearly agreeing with that in Bythocythere. Legs of female 

 likewise rather similar, last pair in male however conspicuously transformed, 

 subprehensile. Caudal lamellae conical in shape, with one rather long apical 

 seta and 2 much shorter lateral bristles. Copulative appendages of male com- 

 paratively large and attached to a fleshy stalk, terminal part well developed 

 and somewhat bent in the middle. 



