RECENT BRITISH OSTRACODA. 



113 



oval, with parallel sides and abruptly tapering obtuse extremities ; over the anterior 

 hinge are two conspicuous polished tubercles, supported on divergent proci— >s or ribs. 

 The whole carapace is surrounded by a fillet, which, on the anterior and ventral aspec is, 

 forms a very broad and stout keel. End view ovate, tumid, very broad below. The 

 surface of the shell is marked with rather large, vaguely defined pits, and is slightly 

 scabrous. Animal unknown. 

 Length -gj in., height -^j in. 



Hab. Channel Isles, 15-30 fathoms (Mr. J. G. Jeffreys) ; Oban (Mr. D. Robertson). 



This is strikingly similar in general contour to 0. Jeffrey sii ; but in other respects the 

 two species are abundantly distinct. It bears also some resemblance to C. marginata 



9 



(Norman) and to certain forms of C. tuberculata. From the last-mentioned it may be 

 at once separated by the conspicuous stalked tubercles of the anterior hinge, the absence 

 of tubercles on the lateral surfaces of the valves, and, as seen from above, by tin* regularly 

 oval contour, without posterior tumidity. Prom C. marginata the hinge-tubercles, 

 characters of surface, and want of excessive angularity of the dorsum sufficiently 



distinguish it. 



24 Cythere marginata, Norman. (Plate XXXI. figs. 5- 



Cythere marginata, Norman, Ann. & Mag. Nat. Hist. vol. ix. (18G2) p. 47, pi. iii. figs. 10-12. 



Carapace subquadrangular, highest in front ; height equal to more than half t be length 

 Anterior margin rounded below, sloping steeply backwards above, and formin 



dorsal extremity a conspicuous angular elevation over the anterior hinge. Inferior 

 margin nearly straight ; dorsal margin sloping sinuously and rather steeply backwards 

 Posterior extremity narrowed, angular, produced below. Outline, as seen from above, 

 oblong, widest in the middle and tapering abruptly at each extremity ; width equal to 

 half the length. End view tumid, ovate. Surface covered with large angular pitting*, 

 which are separated from each other by harrow ribs. Animal unknown. 

 Length -£j in., height ^j in. 



Hab. Lamlash Bay (Rev. A. M. Norman). 



The single specimen npon which this species is founded it scarcely well enough 

 marked in its characters to form a satisfactory species; hut I am unahle to refer it w.tl, 

 certainty to any other described form. 



25. Cythere quadridentata, Baird. (Plate XXXI. figs. 19-30.) 



Cythere quadridentata, Baird, Brit. Entom. p. 173, t. xxi. fig. 2. 



TW v x ^ 4. n + TWnin Treland Bav of Biscav. Fossil— Glacial, Scotland, 



witish type. Distribution : Recent— Great Britain, ireianu, dm u 



n„ xi -a ^innff nnndran<mlar or cuneate, highest m front; 



Carapace, as seen from the side, oblong quadran ^ ^ 



Jaght equal to about one-half the ^J^J^^ Mrr0W ed, angular, 

 bearing a row of from eight to twelve small teeth, posterior u g & 



excavated above and considerably produced below where . « ge*«Qj " " ' 

 about four sharn snines. The inferior margin is stnught or shghtly C°»v«, the 



~~* s P mes ' X11 ° .""Tr* + h °ot> slonins -sinuously backwards. The 

 superior elevated over the anterior hinge, thence siopin e u j 



