FROM WEST PAKISTAN 61 



Material. Six specimens from the below locality from three horizons (sample 

 nos. 460-i, 460-j and 460-0). GSP BM 2574. 



Type locality. Sor Range section. 



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



Description. Sexual dimorphism rather pronounced ; the females are higher and 

 wider than the males. Carapace tapering towards the posterior, subrectangular in 

 side view. Dorsal margin nearly straight in the male dimorph but very slightly 

 convex in the female (appears to be irregular in dorsal view due to ornamentation) ; 

 ventral margin almost straight but concealed by the ventral ridge in side view ; 

 anterior broadly rounded, posterodorsal margin very slightly concave ; postero- 

 ventral margin rounded. Greatest length lies below mid-point, greatest height in 

 the anterior third. Anterior and posterior cardinal angles well-developed. Right 

 valve very slightly over-reaches the left at the anterior margin. Subcentral-tubercle 

 present but not pronounced. Eye-tubercle prominent, rounded and polished. Orna- 

 mentation consists of reticulations and spines. The spines are of variable size. A 

 posterodorsal process consists usually of a large spine, which stands out in lateral 

 view. The ventral ridge is high and with an alar expansion, slightly concave in the 

 middle culminating in the posterior third with a pointed end. Anterior and posterior 

 marginal rims more or less distinct and decorated with a row of spines. Anterior 

 and posterior margins denticulate. Internal characters not seen. 



Dimensions (mm). 



L 

 Io. 3165 Carapace male 0-64 



Io. 4345 Carapace female (holotype) 0-64 



Comparison. Phalcocythere improcera sp. nov. is much smaller, has deeper 

 reticulations and a posteroventral margin slightly drawn out towards the venter. 



Phalcocythere sentosa sp. nov. 



(Plate 32, figs. 4-10) 



Derivation of name. Latin sentosus, rough ; with reference to the surface 

 ornamentation. 



Diagnosis. A species of the genus Phalcocythere in which ventral ridge is present 

 but not high ; surface ornamentation consists of combination of reticulations and 

 papillae ; posterodorsal process a small tubercle or short spine. Subcentral-tubercle 

 distinct, eye-tubercle prominent. 



Holotype. Io. 4346, a male carapace (PI. 32, figs. 4, 5, 8, 10). 



Paratype. Io. 4298. 



Material. 67 specimens from the Rakhi Nala section from 11 horizons (sample 

 nos. 3153, 3165, 3167, 3169, 3170, 3173 to 3177 and 3180) . GSP BM 2575-6. 



Type locality. Rakhi Nala section. 



Type horizon. Upper Rakhi Gaj Shales, sample no. 3167. 



H 



w 



o-37 



0-27 



o-39 



0-32 



