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-vieiv suboval. 



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

 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 Gahcia, and in Tertiary beds 

 of Upper Silesia. 



No. 9. Cythere concinna, sjjcc. nov. Plate IV, figs. 7 a — If. 



INCH. 



Length, Jq 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 ; eiid-vieio narrow-ovate. 



Cythere concinna was found in some numbers — together with Cythere {Ci/theridea) 

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



No. 10. Cythere Woodiana, spec. nov. Plate III, figs. 2« — 2^7- 



INCH. 



Length, J^ Pliocene : Suffolk. 



Carapace oblong, I'ounded 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 cii'cular pits, arranged in longitudinal lines, except on the 

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



