184 



somewhat abruptly bent both in front and behind, ventral margin slightly 

 sinuated in front and nearly straight behind, anterior extremity obliquely rounded 

 off, posterior very distinctly emarginated in the middle, the emargination being 

 bounded above by a somewhat gibbous corner, below by a projecting lobe 

 obtusely truncated at the end; seen dorsally, oblong ovate in outline, greatest 

 width behind the middle and not nearly attaining half the length, side-edges 

 somewhat angular behind, anterior extremity gradually narrowed and sharply 

 pointed at the end, posterior obtusely triangular. Valves very unequal and 

 rather dissimilar in shape, the right one having the dorsal margin much more 

 strongly bowed in the middle than the left, whereas the anterior and posterior 

 angles are nearly obsolete. Surface of shell somewhat uneven, each valve 

 exhibiting behind a well-marked vertical ridge and below it a broad rounded 

 expansion, having moreover in front a few radiating folds; edges smooth and 

 rather densely hairy in front and behind; sculpture well marked, resembling 

 that in the preceding species. Antennae comparatively less robust, than in 

 H. vilLosa, but of a very similar structure; vesicle leading to the flagellum of 

 the posterior ones however much larger and slightly bilobed. 



Male somewhat smaller than female, but having the shell of a rather 

 similar shape. Copulative appendages with the terminal part very sharply 

 defined, and acutely produced both in front and behind. 



Colour of shell dark fuscous. 



Length of adult female 0.80 mm. 



Remarks. The present species is easily recognised by the very con- 

 spicuous emargination on the posterior extremity of the shell, especially strongly 

 marked on the right valve, this character having indeed occasioned the specific 

 name proposed. Otherwise it is rather closely allied to H. villosa, though of 

 rather larger size. 



Occurrence. This is a true northern species. I have only taken it in th 

 fresh state off the Lofoten islands and rather sparingly, whereas it occurre 

 very abundantly in shell-sand from 0xfjord, Finmark. 



Distribution. Arctic Sea, Shetland. 



Fossil. Norway, Scotland. 



86. Hemicythere crenulata, G. O. Sars. 



(PI. LXXXV, fig. 2). 

 Cythereis crenulata, G. O. Sars, Oversigt af Norges marine Ostracoder, p. 39. 



Specific Characters. Female. Shell, seen laterally, oval subreniform i 

 shape, somewhat higher in front than behind, greatest height exceeding half 





