H 



w 



o-44 



0-32 



o-44 



o-44 



FROM WEST PAKISTAN 63 



length passes through mid-point, greatest height in the anterior third and greatest 

 width in the anterior two-fifths. Anterior and posterior cardinal angles protruding. 

 Valves almost equal. Subcentral-tubercle prominent, eye-tubercle distinct and 

 situated below the cardinal angle. Anterior marginal rim distinct, and ornamented 

 with seven very short ridges with small depressions in between (like flutes or scallops), 

 posterior rim more or less distinct. Surface reticulate with a distinct ventral ridge 

 which slopes obliquely upwards posteriorly ending in the posterior third. In many 

 specimens the posterior ending is pointed or spinose. Internal details not determin- 

 able, all specimens being complete carapaces. 



Dimensions (mm). 



L 

 Io. 4343 Carapace male (holotype) o-6o 



Io. 4299 Carapace female 0-56 



Comparison. This species shows some resemblance to Phalcocythere rete sp. nov. 

 but is smaller and has subparallel rather than tapering dorsal and ventral margins. 

 It differs from Phalcocythere improcera sp. nov. and Phalcocythere sentosa sp. nov. in 

 shape and surface ornamentation. 



Remarks. P. dissenta seems to be restricted to the Shales with Alabaster only 

 and has been found in the Rakhi Nala and Zao River sections. It is abundant in the 

 Rakhi Nala section but rare in the Zao River area. 



Phalcocythere spinosa sp. nov. 

 (Plate 33, figs. 1, 2, 7, 8) 



Derivation of name. Latin spinosus, spiny. 



Diagnosis. A species belonging to the genus Phalcocythere with short spines 

 and/or papillae superimposed on reticulations ; ventral ridge distinct and terminating 

 in a spine in posterior third ; posterodorsal process well-marked and blade-like. 



Holotype. Io. 4347, a carapace. 



Material. 16 specimens from the Zao River section from one horizon (sample 

 no. 24161). GSP BM 2579. 



Type locality. Zao River section. 



Type horizon. Upper Chocolate Clays, sample no. 24161. 



Description. Carapace subrectangular in side view. Dorsal margin almost 

 straight, appearing to be irregular in lateral view due to ornamentation ; ventral 

 margin more or less straight but hidden by the ventral ridge in side view ; anterior 

 margin broadly rounded ; posterodorsal margin slightly concave ; posteroventral 

 margin rounded. Greatest length passes through the mid-point and greatest height 

 passes through the anterior cardinal angle. Valves nearly equal. Subcentral- 

 tubercle well-developed, eye-tubercle rounded, distinct and lies below the anterior 

 cardinal angle. Surface ornamentation consists of short spines and/or papillae 

 superimposed on reticulations. A distinct ventral ridge, diagnostic of the genus, 



