26 EARLY TERTIARY OSTRACODA 



River sections is 286 ft. and 378 ft. respectively. Hence, it is a very useful species 

 as a horizon marker in the region. 



Adult specimens in the two sections vary in size and in the strength of 

 ornamentation. 



Genus BRADLEY A Hornibrook 1952 

 Type species. Cythere arata Brady 1880. 



Bradleya ? voraginosa sp. nov. 

 (Plate 12, figs. 3-9) 



Derivation of name. Latin voraginostis, full of pits. 



Diagnosis. A species provisionally placed in the genus Bradleya with sub- 

 parallel dorsal and ventral margins, projecting anterior cardinal angle, truncated 

 posterior, coarsely and deeply reticulate surface. 



Holotype. Io. 4321, a male carapace (PI. 12, figs. 3, 5, 7, 8). 



Paratype. Io. 3115. 



Material, io specimens from the locality below from two horizons (sample 

 nos. 24159 and 24161). GSP BM 2525. 



Type locality. Zao River section. 



Type horizon. Upper Chocolate Clays, sample no. 24161. 



Description. Carapace subrectangular in lateral outline. Valves ventrally 

 inflated. Dorsal and ventral margins almost straight and subparallel, anterior 

 margin broadly rounded, posterior truncated, posterodorsal slope very slightly 

 concave particularly in the right valve. Anterior cardinal angle projecting, posterior 

 cardinal angle rather prominent (approximately 110°). Valves almost equal. Eye- 

 tubercle rounded and distinct and situated just below the anterior cardinal angle. 

 Subcentral-tubercle more or less distinct. A marginal rim runs around the anterior, 

 ventral and posterior margins. It is fairly well-developed anteriorly and posteriorly 

 but is not so prominent along the venter. Surface ornamentation consists of 

 coarse, deep reticulations and dorsal and ventral ridges. 



The dorsal ridge is ill-defined in the anterior half, slightly arched upward in the 

 posterior third culminating in a short horn-like posterodorsal process. The ventral 

 ridge is better developed and slightly alate posteriorly. Anterior margin finely 

 denticulate, posteroventral margin ornamented with 4-5 short spines. Internal 

 details not very well displayed. Duplicature fairly wide. Selvage in the left valve 

 is subperipheral and less well-developed than in the right valve where it is at some 

 distance from the outer margin. It has a deep flange groove, particularly in the 

 venter. Hinge holamphidont ; left valve with a deep almost rounded anterior 

 socket which is bounded on all sides, a conical projecting anteromedian tooth, an 

 apparently denticulate bar and a deep elongate posterior socket which is bounded 

 on the venter. Hinge of right valve not clearly seen. 



