205 



basal part rounded quadrangular in shape and sending off at the junction 

 with the terminal part a posteriorly-curving falciform piece, copulatory string 

 narrowly convoluted at the base, with the extremity pointing backwards; ter- 

 minal part provided at the base in front with a nose-shaped projection, distal 

 part rather produced and narrowly rounded at the tip. 



Colour of shell in its greater extent whitish, semipellucid, but marked in 

 the centre by a very conspicuous sharply defined blackish patch of a saddle- 

 like shape, extending down the sides of the valves. 



Length of adult female 0.44 mm. 



Remarks. The present species is easily distinguished from the preceding 

 ones by the almost quadrangular shape of the shell, and by the protuberance 

 of the hind extremity being located distinctly above the longitudinal axis. 

 When examined in the fresh state, it is moreover easily recognisable by the 

 sharply defined dark saddle-like patch occupying the centre of each valve, a 

 character which indeed has given rise to the specific name proposed. 



Occurrence. I have only met with this form in the upper part of the 

 Christiania Fjord, where some few specimens were taken, many years ago, 

 from a depth of 6 10 fathoms. Norman has however found it also in 2 

 localities on the western coast of Norway. 



Distribution. British Isles, Holland, Fosse de Cap Breton, Bay of Biscay. 



Fossil. Scotland. 



102. Cytherura atra, G. O. Sars. 



(PI. XCV, fig. 2). 

 Cytherura atra, G. O. Sars, Oversigt af Norges marine Ostracoder, p. 75. 



Specific Characters. Female. Shell, seen laterally, oblong subreniform 

 in shape, equally high in front and behind, greatest height scarcely exceeding 

 half the length, dorsal margin gently arched behind, more abruptly bent in 

 front, with a slight indication to an angle in the ocular region, ventral margin 

 slightly sinuated in the middle and terminating behind in a well-marked 

 angular corner, anterior extremity obliquely rounded, posterior only slightly 

 produced, the terminal protuberance being rather short and blunt, located in 

 the longitudinal axis of the shell; seen dorsally, oblong lanceolate in outline, 

 with the greatest width behind the middle and somewhat exceeding l /3 of the 

 length, both extremities pointed, the posterior more abruptly contracted at the 

 end than the anterior. Surface of valves evenly convex, exhibiting a faint 

 reticulate pattern, edges smooth and very sparingly hairy. Anterior antennae 



