152 POST-TERTIARY ENTOMOSTRACA. 



This species differs from C. convexa, Baird {C. punctata ? Miinster) in its greater- 

 proportionate height, in being more tumid below the middle, and in being destitute of any 

 very prominent beak at the postero-inferior angle. In lateral outline it approaches; 

 closely to a recent Mediterranean species, C. Speyeri, Brady,^ but is smaller and very 

 much less tumid, besides being deficient in the beak, which that species possesses in 

 common with C. convexa. 



Distribution. Fossil. — Brick-earth of the Nar ; Hopton Cliff, Yarmouth. Tertiary 

 beds of France and Germany. 



15. Cythere costellata, Homer. Plate XVI, figs. 13 — 15. 



1838. Cytherina COSTELLATA, iJower. Neues Jahrb. Mineral., &c., p. 517, pi. vi,. 



fig. 24 i^fide Bosquet). 

 1850. Cythere costellata, Bosquet. Entom. foss. terr. tertiair. France, p. 58, 



pi. ii, figs. 1 1 a — d. 

 1856. — — Jones. Monog. Tert. Entom., p. 32, pi. v, fig. 11. 



Carapace, as seen from the side, oblong, somewhat cuneiform, much higher in front 

 than behind, height equal to fully half the length, anterior extremity boldly and obliquely 

 rounded, posterior also rounded, but narrow, and bearing in the middle one moderate- 

 sized spine with two or three smaller ones below ; superior margin somewhat angulated 

 in front, behind which it is slightly emarginate and thence slopes backwards almost in a 

 right line, inferior almost straight for the first two thirds of its course, then curved 

 upwards ; seen from above, somewhat lozenge-shaped, greatest width situated behind the 

 middle and equal to half the length, obtusely pointed or almost sub-truncate in front, 

 doubly mucronate behind. Shell dense and strong, marked longitudinally with 

 numerous (10 — 12 on the lateral aspect of each valve) strong, rounded, flexuous ribs; 

 the left valve considerably larger than the right, aud overlapping with a broad flange on 

 the ventral surface of the shell ; hinge-line on the dorsal aspect depressed so as to form a 

 wide sulcus, and sharply bent in front. 

 Length 4^th of an inch. 



Distribution. Fossil. — England : Tertiary beds of Bracklesham, and Pholas-bed of 

 Selsey. Tertiary, Prance. 



Our figures of this species were already lithographed before we became aware that it 

 could not rightly be claimed as belonging to the Post-tertiary Ostracoda. The " Pholas- 

 bed " in which our speuimens were found is certainly of considerably earlier date, unless 

 indeed the Ostracoda which it contains have been washed into it from some older deposit. 



^ Described in * Les Fonda de la Mer,' torn, i, p. 99, pi. xii, figs. 8—10. 



