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1. Polycope orbicularis, G. O. Sars. 



(PI. XIV, PI. XV, fig. 1) 

 Polycope orbicularis, O. O Sars, Oversigt af Norges marine Ostracoder, p. 122. 



Specific Characters. Female. Shell rather tumid, seen laterally, nearly 

 circular in outline, greatest height in the middle and but little inferior to the 

 length, dorsal margin strongly and somewhat angularly arched in the middle, 

 ventral margin forming a more even and rather bold curve, anterior extremity 

 bluntly rounded, with a slight indication to an angle above; -- seen dorsally 

 rather broad, almost rhomboidal in outline, the lateral edges being abruptly 

 curved in the middle, greatest width about equalling 2 /s of the length, anterior 

 extremity somewhat more pointed than the posterior. Valves thin and fragile, 

 though somewhat thickened along the dorsal face; ventral margin exhibiting 

 a narrow hyaline border crossed by a number of very small and delicate 

 spinules. Surface of valves finely punctate and moreover exhibiting a very 

 delicate reticulate pattern of polygonal meshes. Caudal lamellae each armed 

 with 7 claws finely ciliated behind and gradually diminishing in size proximally, 

 all the claws being inserted within deep incisions of the margin, which projects 

 between them as rather prominent triangular processes. 



Male somewhat smaller than female, but otherwise very similar in its 

 outward appearance. Left caudal ramus conspicuously transformed; outermost 

 claw replaced by a thin bristle inserted high up on the side of the lamella, 

 subjacent excavation rather wide, with the anterior defining angle digitiform 

 produced; anterior upturned process broad at the base but rapidly tapered 

 distally and terminating in a tridentate point. Copulatory apparatus of such 

 a complicated structure as only with difficulty to be described in detail, its 

 most conspicuous part being a rather large piece, on the left side, curving 

 upwards in close approximation to the above-mentioned process of the cor- 

 responding caudal lamella, and terminating in a somewhat dilated bilobular 

 extremity. 



Colour of shell pale yellow, variegated with irregular reddish orange patches 

 radiating from the centre of each valve towards the margins. 



Length of adult female amounting to 0.70 mm; that of male to 0.50 mm. 



Remarks. This species, being the first described, ought of course to be 

 regarded as the type of the present genus. It seems to me somewhat questi- 

 onable, if the form recorded under this name by Brady in his Monograph of 

 the recent British Ostracoda is the same species, as the figure he gives of the 

 shell, as seen dorsally, is rather different. On the other hand, the figures given 



