RECENT BRITISH OSTRACODA. 



395 



species, C. albomaculata, convexa, ruhida, smd pulckella, present intermediate characters, 

 and could not be included under either of the genera as defined by Sars. The chief 

 distinctive characters taken by him as the ground of separation are the length of the 

 urticating seta of the lower antenna (which, in the females of " Ci/tJwreis," is exceedingly 

 short), the structure of the mandibular palp, and the abdominal rami. These characters 

 may be tabulated as follows : — 



Cythere, Sars. 



of equal length in male and 

 female. 



composed of three joints, and 

 simply setose; two branchial 



Urticating seta of lower antenna 

 Mandibular palp 



Postabdominal rami 



filaments. 



forming two obtuse lobes. 



Cythereis, Sars. 

 very short in the female. 



composed of four joints, and 

 bearing three strong, curved 

 pectinate setae; five branchial 

 filaments. 



bearing two or more stout ciliated 

 setae. 



If the characters here ascribed to Cythereis could have been shown to be uniformly 

 coincident with the quadrangular and rugose forms of carapace for which the genus 

 Cythereis was originally proposed, or even if tliey could have been applied with precision 

 to any group, without respect to shell-structure, they might perhaps, though dubiously, 

 have been allowed to form the basis of a distinct genus ; but seeing that we have forms 

 distinctly partaking of the characters of both genera, there seems no reasonable course 

 but that of uniting the two under one name. 



C. albomaculata, with the shell-characters and urticating setae of Cythere, has the 

 mandibular palp and abdominal rami of Cythereis. C. convexa is perhaps intermediate 

 in form of carapace, but much more near to Cythere than to Cythereis, while the 

 urticating seta and mandibular palp agree with those of Cythereis. Both species possess 

 further characters (in the lower antennae) which are, so far as I know, peculiar to them- 

 selves. The abnormal characters of C. ruhida and pulchella will be pointed out in the 

 descriptions of those species. 



a. Valves elongate or reniform, punctate, not prominently rugose or spinous. 

 * Mandibular palp three-jointed, simply setose ; urticating seta long, equal in the male and female. 



1. Cythere lutea, Miiller. (Plate XXVIII. figs. 47-56, and Plate XXXIX. fig. 2.) 



Cythere lutea, Miiller, Entomostraca, p. 65, tab. vii. figs. 3, 4; Sars, Oversigt af Norges mar. Ostrac. 



p. 28; Zenker, Anat.-syst. Stud, iiber die Krebsthiere, p. 83, Taf. v. C. 

 reniformis, Baird, Brit. Entom. p. 169, tab. xx. figs. 5, 5 a-f. 



setosa, Brady, Trans. Zool. Soc. vol. v. p. 371, pi. 58. figs. 12 a-c, 13 a-d, 15 a (not 15 b-e). 



Scandinavian type. Distribution : Recent — Baffin's Bay, North Sea, Baltic, Great Britain, Ireland, 

 Mediterranean. Fossil — Raised beaches and glacial clays, Scotland, Ireland, and Norway. 



Carapace reniform, compressed. In female the extremities are obliquely rounded 

 and nearly equal ; the greatest height in the middle, equal to considerably more than 

 half the length. Dorsal margin gently and evenly arched, ventral deeply sinuate, owing 

 to the partial disappearance of a broad flattened flange which borders the extremities 

 and most of the inferior margin. Seen from above, the outline is compressed, oblong 



3 H 2 



