74 EARLY TERTIARY OSTRACODA 



Description. Sexual dimorphism distinct ; the males are more elongate than 

 the females. Carapace subrectangular in lateral outline. Dorsal margin almost 

 straight but appears undulating in side view due to the over-reaching of the dorsal 

 line of ornamentation, ventral margin nearly straight. Anterior margin broadly 

 and evenly rounded, posterior straight, posterodorsal slope almost straight. Left 

 valve slightly over-reaches the right valve in the anterodorsal and posterodorsal 

 corners ; otherwise the two valves are equal. Eye-tubercle distinct, rounded and 

 polished. Subcentral-tubercle prominent and projecting particularly in dorsal and 

 ventral views. Dorsal line of ornamentation consists of three nodes including a large 

 subangular posterodorsal node which extends vertically down for a short distance. 

 Ventral line of ornamentation consists of two nodes but in some specimens it is just a 

 short ridge. A projecting, almost vertical postero ventral ridge runs from behind the 

 ventral line of ornamentation to a point which is slightly above the mid-line. A 

 curved ridge diagnostic of the genus runs from the eye-tubercle to the subcentral- 

 tubercle ; it is not well-marked. The subcentral-tubercle has two faint, short, 

 curved ridges on its ventral side, one to the anterior and one to the posterior. Anterior 

 marginal rim high, extending along the ventral and posterior margins as a less high 

 rim. Anterior margin set with numerous short spines, concealed in lateral view by 

 the elevated anterior marginal rim. There is one short posterodorsal marginal spine 

 and one short posteroventral marginal spine. Internal details not determinable. 



Dimensions (mm). 



L H W 



Io. 4304 Right valve male o-6i 0-34 — 



I°- 4353 Carapace female (holotype) 0-56 0-36 0-32 



Stigmatocythere delineata sp. nov. 

 (Plate 37, figs. 2, 4-10) 



Derivation of name. Latin delineata, outlined ; from the resemblance of the 

 ornamentation to sketch map. 



Diagnosis. A species of the genus Stigmatocythere with a large hexagon formed of 

 ridges in the posteromedian region, dorsal ridge broken in the middle and extending 

 vertically below in the posterodorsal region. 



Holotype. Io. 4356, a female carapace (PL 37, figs. 7-10). 



Paratype. Io. 4305. 



Material. Six specimens from the type locality from two horizons (sample 

 nos. 24154 and 24155). GSP BM 2590-91. 



Type locality. Zao River section. 



Type horizon. Upper Chocolate Clays, sample no. 24154. 



Description. Sexual dimorphism apparent ; the males are proportionally 

 longer than the females. Carapace subrectangular in side view. Dorsal margin 

 slightly concave, ventral margin almost straight, anterior margin broadly and evenly 

 rounded, posterodorsal slope and posteroventral margin nearly straight. Greatest 



