FROM WEST PAKISTAN 19 



the reticulae being arranged in longitudinal lines with weak ridges in between, 

 subcentral-tubercle indistinct, marginal rim low, anterior marginal area compressed. 



Holotype. Io. 4318, a male carapace (PI. 4, figs. 10-13). 



Paratype. Io. 4265. 



Material. Nearly 670 specimens (including adults and juveniles) from the Rakhi 

 Nala section from 10 horizons (sample nos. 3438, 3440, 3443 to 3445, 3448, 3450, 3451, 

 3457 and 3458). One specimen from the Shpalai Khwara section from one horizon 

 (sample no. 24683). GSP BM 2515-6. 



Type locality. Rakhi Nala section. 



Type horizon. Shales with Alabaster, sample no. 3443. 



Description. Carapace ovate in lateral outline and slightly tapering towards the 

 posterior. Sexual dimorphism marked ; the males are longer in proportion than the 

 females. Anterior margin broadly and obliquely rounded, somewhat compressed, 

 posterior almost straight, posteroventral margin slightly curved. Dorsal margin 

 sinuous, ventral margin evenly curved. Valves nearly equal. Subcentral-tubercle 

 indistinct. Eye-tubercle low. Surface ornamentation consists of a combination of 

 reticulations and weak ridges. Anterodorsal furrow deep with a short more or less 

 vertical anterior ridge characteristic of the genus. Marginal rim low. Internal 

 characters unknown. 



Dimensions (mm). 



L H w 



Io. 4318 Carapace male (holotype) 0-54 0-32 0-25 



Io. 4265 Carapace female 0-46 0-30 0-24 



Comparison. The present species differs from Alocopocy there abstracta sp. nov. 

 and Alocopocythere transcendens sp. nov. in being smaller and having weak longitudinal 

 ridges. Moreover, A. longilinea has a low marginal rim and an indistinct sub- 

 central-tubercle. Alocopocythere coarctata sp. nov. is about the same size but has a 

 high marginal rim, well-developed subcentral-tubercle and more sinuous dorsal 

 margin. 



Remarks. A. longilinea occurs in the lower part of the Shales with Alabaster 

 of the Rakhi Nala section and at several horizons it is very abundant. It is very rare 

 in the Shpalai Khwara section. 



Alocopocythere transversa sp. nov. 

 (Plate 5, figs. 4, 5, 7-10 ; Plates 6-8 ; Plate 9, figs. 1-5) 



Derivation of name. Latin transversus, transverse ; with reference to the 

 posterior ridges. 



Diagnosis. A species of the genus Alocopocythere with three posterior transverse 

 concentric ridges. A short ridge in the anteroventral area runs obliquely from the 

 anterior towards the venter, a shallow groove on the dorsal side of the ridge. Surface 

 reticulate (with or without superimposed papillae) or papillose. 



Holotype. Io. 4316, a female carapace (PL 5, figs. 8, 10) ; (PL 6, figs. 1, 2). 



