253 



behind, ventral margin almost straight or very faintly sinuated in front of the 

 middle, both extremities narrowly rounded off at the end; seen dorsally, oblong 

 oval in outline, with the greatest width in the middle and about equal to 2 5 

 of the length, both extremities obtusely pointed. Surface of valves smooth and 

 glabrous, only marked with scattered small puncta, edges very finely hairy. 

 Eye well observable in the living animal, but, as usual, vanishing in preserved 

 specimens. Anterior antennas moderately slender, with the middle joint of the 

 terminal part scarcely longer then the 1st, last joint very narrow and prolonged. 

 Posterior antennae comparatively short and stout, with the dividing suture of 

 penultimate joint located near the end, apical claw rather slender. 1st pair of legs 

 considerably smaller than the other 2, which are nearly of equal length. Caudal 

 lamellae much reduced, with only a single small bristle at the posterior corner. 



Male of rather larger size than female, and having the shell comparati- 

 vely more elongate. Copulative appendages with the basal part broadly sub- 

 quadrangular in shape, terminal part projected forwards, and pronouncedly 

 boot-shaped, being considerably constricted at the base and expanded distally. 



Colour of shell light yellowish, with a broad band of a dark olivaceous 

 hue across the middle, each extremity more or less distinctly tinged with the 

 same colour. 



Length of adult female 0.50 mm., of male 0.58 mm. 



Remarks. This form was first described by the present author as a 

 species of the genus Paradoxostoma, and was subsequently recorded by 

 G. W. Miiller as the type of his genus Cytherois, though under a different 

 specific name (virens). It is readily distinguished from the other 2 species 

 here described by the shape and colour of the shell. 



Occurrence. I have taken this form rather abundantly in the upper part 

 of the Oslo Fjord, as also in several other places on the Norwegian coast. 

 It is a strictly littoral form, being found close to the beach among algae, and 

 not seldom left in tidal pools together with other littoral animals. 



Distribution. British Isles, Pommerania, Mediterranean. 



Fossil. Scotland, Ireland. 



141. Cytherois vitrea, G. O. Sars. 



(PI. CXV, fig. 1). 

 Paradoxostoma vitreum, G. O. Sars, Oversigt af Norges marine Ostracoder, p. 95. 



Specific Characters. Female. Shell, seen laterally, oblong in shape, more 

 tapered in front than behind, greatest height rather behind the middle and 

 not nearly attaining half the length, dorsal margin well arched behind and 



