78 EARLY TERTIARY OSTRACODA 



Material. 287 specimens from the locality below from 49 horizons (sample 

 nos. 3147, 3160, 3162, 3163, 3166, 3167, 3169 to 3171, 3173 to 3175, 3177 to 3180, 

 3183 to 3193, 3197 to 3200, 3401 to 3404, 3407, 3409, 3410, 3415, 3417 to 3422, 3428, 

 3429, 3434 and 3435) . GSP BM 2595-6. 



Type locality. Rakhi Nala section. 



Type horizon. Upper Rakhi Gaj Shales, sample no. 3166. 



Description. Carapace subrectangular in the male dimorph and sub-quadrate in 

 the female. Sexual dimorphy apparent, the males being larger in proportion to the 

 females. Dorsal and ventral margins subparallel (undulating in lateral view because 

 of surface ornamentation) . Anterior margin broadly rounded, posterodorsal margin 

 almost ' straight, posterior extremity somewhat rounded, posterodorsal margin 

 curved. Greatest height at anterior cardinal angle and greatest length in the 

 middle. Valves more or less equal. Eye-tubercle lobate and prominent situated just 

 below a well-developed anterior cardinal angle. Posterior cardinal angle well- 

 marked in the left valve, armed with a node or short spine pointing upwards. Sub- 

 central-tubercle distinct. Both anterior and posterior margins ornamented with a 

 double row of tubercles or very short spines. Surface tuberculate or nodose (oc- 

 casionally tubercles or nodes develop into spines) . Anterior and posterior marginal 

 rim more or less distinct. Hinge holamphidont : left valve with terminal sockets, 

 postjacent conical tooth and median denticulate bar ; right valve hinge compliment- 

 ary (anterior tooth being conical) . Duplicature of moderate width with a submarginal 

 selvage. Other internal details not determinable. 



Dimensions (mm). 



L H W 



Io. 4308 Carapace male o-6i 0-34 0-24 



Io. 4364 Carapace female (holotype) 0-59 0-35 0-28 



Comparison. T. lobuculus is probably related to Cythereis spinellosa Lubimova 

 and Guha (i960) but differs in having a lobate eye-tubercle and a different lateral 

 outline and surface ornamentation. 



Remarks. Specimens of Cythereis spinellosa Lubimova and Guha were not 

 available for comparison, but from the description and figure given by these authors 

 it appears that the eye-tubercle in that particular species is not lobate. 



Trachyleberis (Trachyleberis) bimammillata sp. nov. 

 (Plate 40, figs. 2, 4-11) 



Derivation of name. Latin bimammillata, two-breasted ; with reference to the 

 split subcentral-tubercle. 



Diagnosis. A small species of the subgenus Trachyleberis in which subcentral- 

 tubercle is divided into two horizontally disposed nodes and posterodorsal process 

 consisting of two vertically arranged nodes. 



Holotype. Io. 4363, a male carapace (PI. 40, figs. 2, 8, 10). 



Paratypes. Io. 3155-9. 



