41 



Cytherella abyssorum, G. O. Sars. 



(PI. XVIII & XI X ) 



Cytherella abyssorum, G. O. Snrs, Oversigt af Norges marine Ostracoder, p. 127. 



Syn : Cytherella Beyrichi, Brady. 



, scotica, Brady. 



Specific Characters. Female. Shell much compressed, seen laterally, of 

 a rather regular oval or elliptical shape, with the height somewhat exceeding 

 half the length, dorsal margin straight, ventral very slightly sinuated, both 

 extremities rounded off and nearly equal; seen dorsally, very narrow, almost 

 cuneiform in outline, with the lateral margins scarcely at all bowed, anterior 

 extremity narrowly truncated, posterior abruptly dilated near the end and blunted 

 behind. Left valve much smaller than the right and fringed at its free edges 

 with a thin hyaline border, which fits closely in a groove of the right valve, 

 when the shell is closed. Surface of shell smooth, though exhibiting a some- 

 what dull appearance by numerous well-marked impressed pits, and in fresh 

 specimens clothed with scattered rigid hairs especially at the hind extremity. 

 Anterior antennas with the 1st joint rather massive and provided in front with 

 a number of somewhat unequal bristles, behind with a considerably longer 

 seta, 2nd joint abruptly bent upon the 1st ventrally and carrying in front 3 

 stout distinctly ciliated setae arising close together from a slight prominence 

 of the edge; 3rd joint comparatively simple, being quite unarmed in front and 

 only provided at the end behind with a thin bristle; 4th joint with 2 such bristles 

 and, like the 2nd, carrying in front 3 subequal stout setae attached to a well- 

 marked blunt prominence; 5th joint of a similar structure, though without any 

 bristles behind; 6th joint with only 2 setae in front, but provided at the end 

 behind with a small bristle; terminal joint much narrower than the others and 

 somewhat obliquely truncated at the end, carrying 4 unequal setae, one of them 

 rather small and attached to the anterior edge. Posterior antennae with the 2 

 segments of the basal part forming together generally an abrupt genicular bend, 

 2nd segment somewhat smaller than the 1st, but slightly widening distally and 

 exerted behind to a somewhat projecting corner tipped with 3 slender setae, 

 anterior edge of the segment clothed with tufts of fine hairs; outer ramus about 

 equal in length to that segment and having the proximal joint rather large, 

 quadrangular in shape, distal joint however very small, lamelliform; inner ramus 



6 Crustacea. 



