H 



w 



0-29 



0-27 



0-32 



0-29 



0-29 



■ — ■ 



0-29 



— 



FROM WEST PAKISTAN 13 



Dimensions (mm). 



L 

 Io. 4260 Carapace male 0-51 



Io. 4311 Carapace female (holotype) 0-52 



Io. 3101 Left valve male 0-51 



Io. 3100 Right valve male 0-51 



Remarks. This species is tentatively assigned to the genus Actinocythereis. It 

 differs from the type species of the genus in having a continuous rather than a 

 broken ventral ridge. In addition, the present species is much smaller, has a pitted 

 surface and fewer radial pore canals. 



Genus ALOCOPOCYTHERE nov. 



Derivation of name. Greek alokos, = furrow, opos = eye ; with reference to the 

 furrow behind the eye-tubercle + cythere. 



Diagnosis. Trachyleberididae in which the eye-tubercle is confluent with both 

 the elevated marginal rim and a short almost vertical ridge, delimited posteriorly by 

 a deep furrow. Anterior and posterior cardinal angles protruding in left valve, only 

 anterior cardinal angle protruding in right valve. Posterior cardinal angle of right 

 valve over-reached by protruding cardinal angle of left valve. Dorsal margin 

 humped. 



Type species. Alocopocythere transcendens sp. nov. 



Description. Dimorphic, the males are proportionally longer than the females. 

 Carapace sub-rectangular to sub-quadrate in shape. Dorsal margin in lateral view 

 sinuous, dominated by protruding anterior and posterior cardinal angles, with a 

 hump between, ventral margin evenly curved or almost straight. Anterior margin 

 broadly rounded, posterior straight or very slightly concave in postero-dorsal margin 

 (between posterior cardinal angle and posterior extremity) ; posterior extremity 

 rounded, postero-ventral region rounded or straight. Valves almost equal in size. 

 Sub-central tubercle and eye-tubercle more or less distinct. Surface ornamentation 

 either reticulate (with or without superimposed lineations or with superimposed 

 papillae) or papillose. A marginal rim always present, usually upstanding anteriorly, 

 less high along venter and posterior. Anterior and posterior margins ornamented 

 with small spines or denticles. Normal pores simple, widely spaced. Radial pore 

 canals simple, almost straight, often slightly inflated towards the middle, tending to 

 occur in groups of two or three, often apparently crossing one another, about 32-35 

 anteriorly and 18-20 posteriorly. Inner margin and line of concrescence coincide. 

 Duplicature of moderate width. Selvage well-marked — sub-peripheral in left valve 

 but at some distance from the outer margin in the right valve. Right valve with a 

 deep flange groove on the centre and anterior. Muscle scar pattern consists of four 

 adductors in a vertical row situated on the posterior margin of the muscle scar pit 

 and an oval frontal scar with two more or less rounded mandibular scars below. 

 Hinge holamphidont. Right valve with highly projecting, stirpate anterior tooth, 



