230 



the shell near the ventral face. Anterior antennae of the usual structure. 

 Posterior antennae with the dividing suture of penultimate joint imperfectly 

 defined. Legs moderately slender, last pair with the 1st joint of the terminal 

 part about the length of the other 2 combined. 



Colour of shell whitish. 



Length of adult female 0.58 mm. 



Male unknown. 



Remarks. The present species is easily recognised from those described 

 in the preceding pages by the almost circular shape of the shell, as seen 

 dorsally, a character which indeed has given rise to the specific name 

 proposed. 



Occurrence. I have taken this form occasionally in the upper part of the 

 Oslo Fjord, as also at Ris0r, south coast of Norway. Norman records it more- 

 over from Lervik, Hardanger Fjord. 



Distribution. British Isles. 



124. Cytheropieron testudo, G. O. Sars. 



(PI. CVI, fig. 1). 

 Cytheropteron testudo, G. O. Sars, Chr. Vid. Selsk. Forh. 1869, p. 29. 



Specific Characters. Female. Shell moderately tumid, seen laterally, short 

 oval or somewhat pyriform in shape, greatest height a little in front of the 

 middle and about equal to 3 /s of the length, dorsal margin boldly arched and 

 sloping rather steeply both in front and behind, ventral margin scarcely at all 

 sinuated, being gently convex thoughout, anterior extremity obliquely rounded, 

 posterior drawn out to a very narrow and prominent caudiform projection 

 located somewhat below the longitudinal axis of the shell: seen dorsally, 

 suboval in outline, with the greatest width nearly equal to the height, side- 

 edges evenly curved, anterior extremity only slightly contracted and remark- 

 ably blunt at the end, posterior tapered to a narrow conical prominence. 

 Valves of rather firm consistency and but little pellucid, with the surface evenly 

 convex and closely punctate, being moreover marked with scattered small 

 tubercles; alaeform expansions rather slight, in the form of evenly curved 

 borders flanking the shell near its ventral face. Limbs on the whole quite 

 normal in structure. 



Colour of shell opacous white. 



Length of adult female 0.50 mm. 



Male unknown. 



