THE TERTIARY FORMATION. 29 



Carapace small, oblong, depressed, flattest anteriorly ; obliquely rounded in front, 

 semicircular behind ; upper and lower margins slightly incurved ; extremities bearing 

 slightly raised marginal rims : surface roughened with irregular punctations. 



Dorsal aspect elongate-acute-ovate ; end-view suboval. 



Two specimens of this minute species (which agrees with Reuss's C. Kostelenxi*, 

 except in the condition of the posterior margin) were found by Mr. Rosser in the 

 Woolwich beds (Lower Eocene). C. Kostelensis occurs in the Leitha-Kalk of Moravia 

 and Austria, in clay-beds near Vienna, in the salt-rock of Galicia, and in Tertiary beds 

 of Upper Silesia. 



No. 9. Cythere concinna, spec. nov. Plate IV, figs, la — If. 



INCH. 



Length, ^ Pleistocene : Bridlington, Yorkshire. 



Carapace triangular-oblong ; rounded in front, obliquely truncate behind ; straight 

 on the ventral, and obtusely angular on the dorsal border, the anterior hinge forming 

 a low blunt angle : surface of valves depressed ; marked by three low tubercles (one 

 central and two posterior), minutely punctated, and perforated at points as wide apart 

 as the distance of 3 — 4 of the superficial pits (fig. If) ; the valves have also a slightly 

 elevated anterior margin, and are sometimes beset with obscure scattered tubercles, 

 forming an irregular rugosity of the surface. 



Dorsal aspect narrow-oblong with rounded ends ; end-view narrow-ovate. 



Cythere concinna was found in some numbers — together with Cythere {Cytheridea) 

 Sorbyana — by Mr. H. C. Sorby in the Bridlington Crag, at Bridlington, Yorkshire. 



No. 10. Cythere Woodiana, spec. nov. Plate III, figs. 2 a — 2y. 



INCH. 



Length, T x ff Pliocene : Suffolk. 



Carapace oblong, rounded obliquely at the extremities, upper and lower borders 

 nearly straight; valves depressed anteriorly, most convex just behind the centre and 

 towards the ventral border ; right valve markedly narrower than the left ; its hinge- 

 line outstanding, being notched fore and aft : surface ornamented with small well- 

 marked sub-hexagonal or circular pits, arranged in longitudinal lines, except on the 

 anterior portion of the valves, where the pitting affects transverse and concentric lines ; 



