FROM WEST PAKISTAN 17 



Alocopocythere by its anterodorsal groove, which is not only delimited by an anterior 

 ridge but by a posterior ridge as well. 



Remarks. This is so far the oldest known species of the genus Alocopocythere. 

 It occurs abundantly in one horizon (sample no. 31 11) of the Gorge Beds of the Rakhi 

 Nala section, the male to female ratio being 1:3. 



Alocopocythere abstracta sp. nov. 

 (Plate 3, figs. 5-11 ; Plate 4, fig. 1) 



Derivation of name. Latin abstr actus, separated, referring to the difficulty in 

 separating this species from A. transcendens because of the many intermediate 

 forms. 



Diagnosis. A reticulate Alocopocythere with straight postero-ventral margin in 

 lateral outline. Subcentral-tubercle present but not prominent. 



Holotype. Io. 4312, a female carapace (PL 3, figs. 9-11) ; (PI. 4, fig. 1). 



Paratype. Io. 4263. 



Material. Over 2600 specimens (including adults and juveniles) from the Rakhi 

 Nala section from 69 horizons (sample nos. 3147, 3152, 3153, 3157 to 3180, 3183, 

 3184, 3186 to 3191, 3193 to 3194, 3197 to 3200, 3401 to 3405, 3407, 3409, 3410, 3415 

 to 3424. 3426, 3428, 3429. 3432, 3434. 3435. 3438, 3443 and 3445). 5 specimens from 

 the Zao River section from one horizon (sample no. 24127). GSP BM 2511-2512. 



Type locality. Rakhi Nala section. 



Type horizon. Upper Rakhi Gaj Shales, sample no. 3163. 



Description. Carapace subrectangular in side view. Sexual dimorphism rather 

 pronounced ; the males are longer than the females. Dorsal margin sinuous, ventral 

 margin nearly straight. Anterior margin broadly and evenly rounded, postero- 

 dorsal margin very slightly concave ; posterior extremity rounded ; postero-ventral 

 margin straight. Anterior and posterior cardinal angles protruding. Valves more 

 or less equal. Eye-tubercle distinct. Subcentral-tubercle present but not pronounced. 

 Surface reticulate. Anterodorsal furrow deep, bounded anteriorly by a short 

 almost vertical ridge diagnostic of the genus. Anterior and posterior margins 

 denticulate, although the denticles are only present in a few specimens. Internal 

 details not known. 



Dimensions (mm). 



L H W 



Io. 4263 Carapace male o-66 0-38 0-34 



Io. 4312 Carapace female (holotype) 0-63 0-39 0-35 



Comparison. Alocopocythere coarctata sp. nov. is smaller than the present species 

 and has a combination of reticulations and weak ridges and a more sinuous dorsal 

 margin. Alocopocythere radiata sp. nov., however, is larger, has deeper reticulations 

 and a better developed subcentral-tubercle having posterior radial ridges. 



A. abstracta has already been compared with Alocopocythere transcendens sp. nov. 



