RECENT BRITISH OSTRACODA. 



413 



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

 hinge are two conspicuous polished tubercles, supported on divergent processes or ribs. 

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

 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 in., height in. 

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



This is strikingly similar in general contour to C. Jeffreysii ; but in other respects the 

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

 (Norman) and to certain forms of C. tuherciilata. Erom 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 the regularlj'" 

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

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

 distinguish it. 



24. C.YTHERE MARGINATA, Norman. (Plate XXXI. figs. 5-8.) 



Cythere marginata, Norman, Ann. & Mag. Nat. Hist. vol. ix. (186.2) p. 47, pi. iii. figs. 10-12. 



Carapace subquadrangular, highest in front ; height equal to more than half the length. 

 Anterior margin rounded below, sloping steeply backwards above, and forming at its 

 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 pittings, 

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



Length ^ in., height in. 

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



The single specimen upon which this species is founded is scarcely well enough 

 marked in its characters to form a satisfactory species ; but I am unable to refer it with 

 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. 



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



Carapace, as seen from the side, oblong quadrangular or cuneate, highest in front ; 

 height equal to about one-half the length. Anterior border obliquely rounded, often 

 bearing a row of from eight to twelve small teeth. Posterior margin narrowed, angular, 

 excavated above and considerably produced below, where it is generally armed with 

 about four sharp spines. The inferior margin is straight or slightly convex, the 

 superior elevated over the anterior hinge, thence sloping sinuously backwards. The 



