38 EARLY TERTIARY OSTRACODA 



pattern consists of four adductors in a vertical superposition and two more or less 

 rounded frontal scars. 



Dimensions (mm). 



L H W 



Io. 4279 Carapace male 078 0-45 0-37 



Io. 4330 Carapace female (holotype) 076 0-49 0-39 



Comparison. Echinocythereis (Scelidocythereis) rasilia sp. nov. although smaller 

 than the present species may be ancestral but has a smooth rather than a papillose 

 surface. Moreover, it has a concavity behind the anterior cardinal angle and lacks 

 the distinct marginal rims. 



Remarks. Echinocythereis (Scelidocythereis) sparsa has so far only been found in 

 the Upper Chocolate Clays of the Zao River area. 



Genus GYROCYTHERE nov. 



Derivation of name. Greek gyros, circle ; with reference to the concentric 

 arrangement of the ornamentation + cythere. 



Diagnosis. Reticulate Trachyleberididae with three or four longitudinal ridges, 

 the dorsal ridge distinct from the eye-tubercle, arcuate, sloping down towards 

 anterior and terminating below the eye-tubercle ; the third ridge more or less distinct 

 in different species. 



Type species. Gyrocythere exaggerates sp. nov. 



Description. Sexual dimorphism rather pronounced ; the females are shorter, 

 higher and wider than the males. Carapace subrectangular to subquadrate in 

 lateral view. Valves almost equal. Eye-tubercle and subcentral tubercle present, 

 more or less pronounced. Surface reticulate. Three to four longitudinal ridges 

 present ; the dorsal ridge commences anteriorly below the eye-tubercle and is arched 

 convexly upwards ; the second ridge stretches backwards from the subcentral- 

 tubercle and is also arched convexly upwards, its continuation in front of the sub- 

 central-tubercle being less pronounced ; the third ridge situated below the sub- 

 central-tubercle slopes obliquely upwards towards the posterior and is curved con- 

 vexly downward towards the anterior and the ventral ridge is confined to the 

 posterior two-thirds of the carapace and culminates in a slight alar expansion in the 

 posterior, almost obsolete or absent in some species. Normal pores simple, fairly 

 numerous. Radial pore canals simple, irregularly spaced, more or less straight, a few 

 seem to bifurcate, approximately 25 anteriorly. Inner margin and line of concresc- 

 ence coincide. Duplicature moderately wide. Selvage well-marked, submarginal 

 in left valve but at some distance from the outer margin in right valve. Ventral 

 and anterior flange grooves well-developed in right valve. Hinge holamphidont 

 with stirpate anterior tooth in right valve. Muscle scar pattern consists of four 

 adductor scars in an almost vertical row and a U-shaped frontal scar, which opens to 

 the anterodorsal angle. 



Comparison. This genus differs from the genus Costa in having an arcuate dorsal 



