70 EARLY TERTIARY OSTRACODA 



Description. Carapace subrectangular in lateral outline. Sexual dimorphy 

 apparent ; the males are longer, less high and less wide than the females. Left valve 

 slightly over-reaches the right in the region of the anterior cardinal angle and at the 

 posterodorsal slope. Subcentral node and eye-tubercle distinct. Surface reticu- 

 late, spiny, or a combination of reticulations and spines or with only one to three 

 longitudinal ridges or lines of ornamentation. The dorsal ridge or line when 

 developed may be straight or arched convexly upwards. A strongly curved ridge, 

 diagnostic of the genus, runs from the eye-tubercle to the anterodorsal corner of the 

 subcentral complex and this may be continued posteriorly either as a ridge or a line 

 of tubercles. The anterior marginal rim also springs from the eye-tubercle and is 

 more or less elevated in the anterior region, continuing as a less elevated rim round 

 the venter and posterior margins. A ventral ridge or line of tubercles diverges 

 posteriorly from the ventral marginal rim. Anterior and posterior margins spinose. 

 Normal pore canals simple, medium, some 60 in the female left valve. Radial pore 

 canals simple, straight, irregularly spaced, some crossing one another, 24-26 anteriorly. 

 Inner margin and line of concrescence coincide. Anterior duplicature moderately 

 wide. Selvage well-marked in both valves, submarginal in the left valve but almost 

 in the outer third of the duplicature in right valve. In right valve a well-developed 

 flange groove is present along the ventral margin and around the anterior margin. 

 Muscle scars consist of four adductor scars in an almost vertical column with an oval 

 frontal scar. Hinge holamphidont ; right valve hinge with a strongly projecting 

 anterior tooth followed by anteromedian socket, posteromedian locellate groove 

 present or reduced to a narrow shelf, a posterior tooth, projecting reniform orpessular. 

 Left valve hinge with anterior and posterior sockets, a conical anteromedian tooth and 

 a posteromedian denticulate or almost smooth bar. 



Comparison. Stigmatocythere differs from the genus Gyrocy there in the arrange- 

 ment of the longitudinal ridges and by having a strongly curved ridge connecting the 

 eye-tubercle and the subcentral-tubercle. The anterior marginal rim is less evident 

 in Gyrocythere while it is well developed in Stigmatocythere. Costa has three or four 

 continuous longitudinal ridges, the median or second of which has a characteristic 

 posterior termination absent in Stigmatocythere and lacks the anterior connection 

 to the eye-tubercle present in Stigmatocythere. Bradley a has only dorsal and ventral 

 ridges. Carinocythereis Ruggieri 1956 has a V-shaped frontal scar and small vesti- 

 bules, characters not found in Stigmatocythere. 



Remarks. Stigmatocythere is so far only known from the Middle and Upper 

 Eocene of the Sulaiman Range. 



Stigmatocythere obliqua sp. nov. 

 (Plate 35, figs. 1-10 ; Plate 36, figs. 1-2) 



Derivation of name. Latin obliqua, oblique ; with reference to the ventral 

 ridge. 



Diagnosis. A strongly reticulate species of Stigmatocythere with three well- 

 developed longitudinal ridges including an oblique ventral ridge. 



