170 



Occurrence. This species, though very common off the British Isles, is 

 rather rarely met with on the Norwegian coast. I have only taken a few spe- 

 cimens at Risor, south coast of Norway, in the laminarian zone, and Norman 

 has recorded it, likewise quite occasionally, from Lervik in the outer part of 

 the Hardanger-Fjord. 



Distribution. British Isles, Iceland, Bay of Biscay. 



Fossil. Scotland. 



75. Cythere viridis, O. Fr. Muller. 



(PI. LXXVIII, fig. 2.) 



Cythere viridis, O. Fr. Muller, Entomostraca, p. 64, PI. VII, figs. 1, 2. 

 Syn: Cythere cyamos, Norman. 



Specific Characters. Female. Shell very short and compressed, seen 

 laterally, rounded quadrangular in shape, somewhat higher in front than behind, 

 greatest height about equal to s /-o of the length, dorsal margin somewhat gib- 

 bous in the ocular region and sloping obliquely behind with an almost straight 

 course, ventral margin distinctly sinuated in the middle and curving evenly 

 upwards behind, anterior extremity broadly and somewhat obliquely rounded, 

 posterior a little narrower and obtusely truncated; seen dorsally, oblong oval 

 in outline, with the greatest width about equal to 2 /5 of the length, sides nearly 

 parallels in the middle, anterior extremity more narrowly pointed than the 

 posterior. Surface of valves closely punctate, with scattered very small tubercles, 

 marginal zone rather narrow and finely striated, anterior and posterior edges 

 clothed with short hairs. Anterior antennae with the terminal part twice as 

 long as the distal segment of the basal one, last joint very narrow and produced, 

 being fully as long as the middle one. Legs comparatively more slender than 

 in the 2 preceding species. 



Male. Shell less high than in female; with the anterior extremity m< 

 bowed below and the ventral sinus deeper. Copulative appendages coi 

 paratively of smaller size than in the 2 preceding species, with the termin. 

 part evenly rounded off at the end, basal part sending off from its infero-posteal 

 corner a slender process pointing forwards, and provided inside with a freely 

 projecting chitinous string curved in the form of a circle. 



Colour of shell light brownish, with a more or less distinct olivaceous 

 tinge; limbs colourless. 



Length of adult female scarcely exceeding 0.50 mm., of male about 

 the same. 



