RECENT BRITISH OSTRACODA. 



399 



two curved transverse furrows ; colour reddish, brown. Animal precisely like that of C. 

 pellucida. 

 Length ^2 



Hab. Chiefly in the brackish water of estuaries and salt marshes. Girdler sand^ Thames, and at Tweed- 

 mouth [Mr. E. C. Davison) ; in salt marshes at Hylton on the Wear, Jarrow on the Tyne, Seaton 

 Sluice, and at the mouths of the Wansbeck and Alne, Northumberland [G. S. B.). 



The great similarity between this and the foregoing species caused me, until very 

 recently, to regard the one as a merely littoral or brackish-water variety of the other. 

 I have been induced to alter that opinion, chiefly by finding, in a gathering from the 

 Girdler sand in the estuary of the Thames, the two forms living together abundantly, 

 and retaining very perfectly their distinctive characters. The points which may be 

 chiefly relied on as characterizing C. castanea are, the more arcuate dorsal margin and 

 greater comparative height of the female, the median position of the greatest width of 

 the carapace, and, in the male, the perfectly straight dorsal margin, and much-narrowed 

 hinder extremity — lastly, the sculpture of the shell-surface, which consists of closely set 

 rounded (not oblong) impressions. The list of habitats here given is doubtless very 

 imperfect ; the species must often have been passed by without special notice as a form 

 of C. pellucida. 



5, Cythere tenera, n. sp. (Plate XXVIII. figs. 29-32.) 



British type. Distribution : Recent — Great Britain, Bay of Biscay. Fossil — Glacial, Norway. 



Carapace of female almost exactly similar in form to C pellucida, but much smaller, 

 the superior margin somewhat more arched ; the surface smooth and having no trace of 

 any transverse sulcus. The shell is very closely and delicately punctate, and bears a few 

 distant and minute elevated papillae. The length is rather more than twice the height. 

 The outline as seen from above is regularly ovate. Animal unknown. Colour white. 

 Shell of the male narrower, and tapered posteriorly. 



Length in. , JU tsf,.^ 



Hab. Ofi" Seaham Harbour, Durham, 15 fathoms (G. S. B.) ; Race's bank and Girdler sand, Thames 

 {Ml-. E. C. Davison) ; the Minch {Rev. A. M. Norman) ; Shetland [Mr. D. Robertson) . 



This species is easily distinguished from C. pellucida by its much smaller size, very 

 fine punctation, and absence of furrowing. There can, I think, be no doubt of its 

 specific rank : all the specimens I have seen are uniform in size, and I have observed 

 no forms intermediate in character between it and either of the two preceding species. 

 The young of C. pellucida, even in their very early stages, are quite coarsely punctate, 

 and those of C. castanea are mostly also of dark colour. 



6. Cythere badia, Norman. (Plate XXIX. figs. 56-59.) 



Cythere badia, Norman, Ann. & Mag. Nat. Hist. vol. ix. (1862) p. 48, pi. iii. figs. 13-15. 

 cicatricosa, Sars, loc. cit. p. 33. 



? canaliculata, Brady, Trans. Zool. Soc. vol. v. p. 373, pi. 59. fig. 4 a-f. 



British type. Distribution : Recent — Norway, Great Britain and Ireland, Mediterranean, Australia ? 

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



