RECENT BRITISH OSTRACODA. 



415 



This species bears considerable resemblance to Prof. T. Ej. Jones's figures of C. retifas- 

 tigiata, but a reference to the type specimens, kindly placed at my disposal by that 

 author, convinces me that the two species are quite distinct. The more elongated forms 

 figured at 31 and 36 are very probably, as in other species, the males ; but I have not 

 been able to satisfy myself of this, all the specimens which I have examined having 

 proved to be only empty shells. 



27. Cythere mirabilis, nov. sp. (Plate XXIX. figs. 7, 8.) 



Distribution : Recent — Scotland. Fossil — Glacial, Scotland. 



Valves, as seen from the side, subtrapezoidal, highest at the anterior third ; greatest 

 height equal to two-thirds of the length. Anterior extremity broadly and obliquely 

 rounded, its lower half bearing a series of short blunt teeth ; posterior narrow, very 

 slightly curved, bearing four teeth at the lower angle ; superior margin sloping steeply 

 and in a convex line from before backwards, terminating abruptly in an obtuse angle at 

 each extremity, more or less abruptly undulated or emarginate throughout, but especially 

 behind the anterior extremity, where it is twice or thrice deeply and irregularly jagged ; 

 inferior margin evenly convex. Outline, as seen from above, ovate, twice as long as 

 broad, obtusely toothed and mucronate behind, margins irregularly spinous and emar- 

 ginate. Hinge-joint very strongly developed, consisting in the right valve of a triangular 

 tooth in front and an obliquely truncate one behind ; in the left of a strong central bar 

 ending abruptly behind, and elevated into an angular tooth in front. Surface of the 

 shell covered in its central and middorsal portions with large angular excavations, and 

 surrounded on the ventral margin and the extremities by wide and sharply cut irre- 

 gularly concentric furrows, across which the separating ribs anastomose sparingly. 



Length 2V in. 

 Hab. Off Lumpan Head, Lewis {Admiralty/ soundings) . 



I have seen only one valve of this species in a recent state ; some of the details above 

 given are taken from fossil specimens obtained from the Scotch Glacial clays. 



28. Cythere mucronata (G. O. Sars). (Plate XXVI. figs. 34, 34«.) 

 Cythereis mucronata, G. O. Sars, loc. cit. p. 48. 



spinosissima, Brady, Trans. Zool. Soc. vol. v. p. 386, pi. Ix. figs. lOa-e. 



Scandinavian type. Distribution : Recent — Norway, Shetland. 



Valves, as seen from the side, subquadrangular, highest in front of the middle ; greatest 

 height equal to half the length. Anterior margin rounded, fringed with six very broad, 

 strong, linguiform, obtusely rounded spines ; posterior narrower, fringed also with a series 

 of about nine much smaller and abruptly truncated spines ; superior margin arched, 

 irregularly emarginate, inferior nearly straight. The central portion of the valves is 

 closely beset with large, clumsy, irregularly angular protuberances, which, towards the 

 extremities, are much fewer and smaller ; along the ventral margin they form a row of 

 stout tooth-like spines, the last of which projects strongly outwards and backwards. 



