FROM WEST PAKISTAN 



35 



Element 

 Anterior 



Anteromedian 



Posteromedian 



Posterior 



Dimensions (mm) 



Left valve 



Deep, almost rounded 

 socket bounded on all 

 sides. 



Projecting subcorneal 

 tooth. 



Slightly projecting 

 denticulate ridge (den- 

 ticles are seen only in 

 nicely preserved 

 specimens) . 

 Deep elongate socket 

 unbounded on venter. 



Right valve 

 Highly projecting 

 pessular tooth. 



Socket opening into 

 posteromedian groove. 

 Locellate groove. 



Large subpessular tooth, 

 less high on anterior. 



Io. 4328 Carapace male (holotype) 



Io. 3134 Carapace female 



I°- 3 I 33 Left valve female 



Io. 4277 Right valve female 



L 

 0-85 

 0-83 

 0-84 

 0-83 



H 

 0-50 



0-51 



o-54 

 0-50 



w 



o-45 



0-48 



Comparison. Echinocythereis (Scelidocythereis) sparsa sp. nov. is smaller than the 

 present species, has a different lateral outline, distinct marginal rims and scattered 

 tubercles as surface ornamentation. In addition to this, it has an indistinct rather 

 than prominent subcentral-tubercle. 



Remarks. This species occurs in the Upper Chocolate Clays of the Zao River and 

 Rakhi Nala sections. It has a short vertical range and hence can be used as an index 

 marker. 



Echinocythereis (Scelidocythereis) sp.A 

 (Plate 17, figs. 3, 4, 8, 9) 



Figured specimen. Io. 3129. 



Material. Two specimens from the locality and horizon below. 



Locality. Sor Range section. 



Horizon. Upper Palaeocene, sample no. 460-i. 



Description. Carapace short, subquadrate in lateral view. Dorsal margin 

 slightly irregular due to surface ornamentation, ventral margin almost straight, 

 anterior broadly and evenly rounded, posterodorsal margin straight, posterior 

 extremity somewhat rounded, posteroventral margin curved. Greatest length lies 

 below mid-point, greatest height in the anterior third and greatest width behind the 

 middle. Anterior and posterior cardinal angles well-developed. Valves almost 

 equal. Eye-tubercle rounded, polished and distinct. Subcentral-tubercle present but 

 not well-developed. Surface reticulate with superimposed papillae. A weak ventral 

 ridge at some distance from the ventral margin slopes obliquely upwards towards the 



