32 EARLY TERTIARY OSTRACODA 



centrically arranged in some species) or almost smooth. Muscle scars are in a 

 vertical column of four adductors with two frontal scars. 



Type species. Cythereis garetti Howe and McGuirt 1935. 



Subgenus ECHINOCYTHEREIS sensu stricto 

 Diagnosis. Echinocythereis without ventral ridges. 



Echinocythereis (Echinocythereis) contexta sp. nov. 

 (Plate 15, figs. 7, 8, 10, 13) 



Derivation of name. Latin contextus, joined together ; from the ornamentation 

 of the papillae joined by the walls of the reticulae. 



Diagnosis. A species of the subgenus Echinocythereis in which posterior end is 

 obliquely rounded towards posterodorsal corner, eye-tubercle prominent, surface 

 reticulate with superimposed papillae. 



Holotype. Io. 4326, a female carapace (PI. 15, figs. 8, 13). 



Paratype. Io. 4276. 



Material. Five specimens from the Sor Range section from four horizons 

 (sample nos. 460-f, 460-i, 460-j and 460-0). GSP BM 2532-3. 



Type locality. Sor Range section. 



Type horizon. Upper Palaeocene, sample no. 460-i. 



Description. Sexual dimorphism rather strong ; the carapace is subrectangular in 

 the male and subquadrate in the female. Dorsal margin in lateral outline un- 

 dulating because of ornamentation, ventral margin almost straight, anterior broadly 

 and evenly rounded. Greatest length passes above the mid-point, greatest height 

 in the anterior fourth and greatest width behind the middle. Anterior and posterior 

 cardinal angles well-developed. Left valve larger than the right, over-reaching 

 it at the anterior, ventral and posterodorsal margins. Eye-tubercle rounded and 

 prominent, standing out from the shell surface in lateral and dorsal views. Sub- 

 central-tubercle more or less distinct. Surface ornamentation consists of slightly 

 papillose reticulae which are concentrically arranged near the margins. Anterior 

 and posterior margins are set with a double row of papillae ; those on the posterior 

 are larger, and in some specimens become short spines. Internal details not seen. 



Dimensions (mm). 



L 

 Io. 4276 Carapace male 0-78 



Io. 4326 Carapace female (holotype) 071 



Comparison. Unlike E. (E.) contexta sp. nov. Echinocythereis (Scelidocythereis) 

 sp.A has a straight rather than curved posterodorsal margin and less prominent 

 eye-tubercles. Moreover, it has a weak ventral ridge and a short horn-like postero- 

 dorsal process. Echinocythereis (Echinocythereis) elongata sp. nov. also differs by 

 possessing a very elongate carapace and a better developed subcentral-tubercle. 



H 



w 



0-44 



o-37 



0-46 



0-42 



