FROM WEST PAKISTAN 87 



Alocopocythere transcendens sp. nov., which ranges up from the underlying Units III 

 and IV, is replaced by A. transversa sp. nov. just above the middle of the lower part 

 of the Upper Chocolate Clays. This last species has several morphotypes ; in the 

 upper part of the Upper Chocolate Clays the papillose form becomes more common 

 and in the Pellatispira Beds this is the only morphotype present. Stigmatocy there 

 obliqua sp. nov., which was very abundant in the underlying biostratigraphic Unit 

 IV, is replaced by the larger Stigmatocythere portentum sp. nov., which has only been 

 found in the uppermost part of the Lower Chocolate Clays. Higher up in the 

 succession, i.e. in the lower part of the Upper Chocolate Clays the place of S. porten- 

 tum is taken by Stigmatocythere lumaria sp. nov. which ranges up into the Pellatispira 

 Beds. The genera Cytherella, Cytherelloidea, Krithe, and Paijenborchella are repre- 

 sented by several species. The genus Gyrocythere nov. has two species in the Unit. 

 Gyrocythere perfecta sp. nov. occurs in the uppermost part of the Lower Chocolate 

 Clays but in the lower part of the Upper Chocolate Clays it is replaced by the larger 

 Gyrocythere exaggerata sp. nov. The subgenera Scelidocythereis nov. and Paracosta 

 nov. are represented by two and three species respectively. Paracosta is known so far 

 only from this Unit. The following are some of the most important species of the 

 Unit : Bairdoppilata sp.A, Cytherelloidea cf. C. costatruncata Lubimova and Mohan, 

 Cytheromorpha sp.A, Cytheropteron sp.D, Alocopocythere transversa sp. nov. (with six 

 morphotypes), Patagonacy there ? nidulus sp. nov., Stigmatocythere lumaria sp. nov. 

 (with two morphotypes) and Trachyleberis (Acanthocythereis) decoris sp. nov. 



Zao River Section 



The two biostratigraphic Units IV and V of the Rakhi Nala section are found in 

 the Zao River section (see Table 5). 



Ostracod Biostratigraphic Unit IV, Lower Eocene (upper part) 



This is very similar to biostratigraphic Unit IV of the Rakhi Nala section. The 

 base of the Unit has been taken arbitrarily at the base of the four foot limestone, 

 which lies 332 ft. below the base of the Platy Limestone. The actual base of the Unit, 

 or the Shales with Alabaster, probably lies much lower in the succession, but sediments 

 below the 4 ft. limestone have not been analysed. These have been recorded as the 

 undifferentiated Ghazij by the collectors. No megafossils have so far been recorded 

 from these sediments and it is unlikely that these would yield any smaller foramini- 

 fera or ostracods because of their lithology — mostly silty shales. 



Ostracods have been found in the upper part of the Unit at two horizons (samples 

 24107 and 241 10). They are extremely abundant in 24107. Approximately half 

 of the Rakhi Nala species of the Unit are found in the Zao River section. None of 

 the species range up into Unit V. Stigmatocythere obliqua sp. nov. is the most 

 dominant species and makes about one-third of the ostracod fauna. Neocyprideis ? 

 sp.B, Neocyprideis sp.C, Pontocyprella sp.B, Pontocyprella sp.C, Xestoleberis sp.C, 

 Xestoleberis sp.D, Xestoleberis sp.E, Genus C sp.i and Genus C. sp.2 are some other 

 important species. 



