The Invertebrate Fauna of the Uitenhage Series. 23 



same genus which occur in the Uitenhage beds and in order to 

 broaden the foundation for future work. 



From statements made in the Eeports mentioned above, it seems 

 that in our present state of knowledge no satisfactory subdivision of 

 the Uitenhage beds is possible, and that the members of the series 

 are so variably developed that no consistent nomenclature is to be 

 hoped for until detailed mapping can be carried out. Of the sub- 

 divisions hitherto employed, the uppermost member of the series, 

 the Sunday's Eiver or Marine Beds, has yielded the majority of the 

 Mollusca which are discussed in this paper. The underlying 

 "Wood Bed" series has also furnished a few species of marine 

 molluscs in addition to Unio and remains of fossil plants. The so- 

 called Enon Beds represent the lowest division of the formation in 

 this district. Messrs. Eogers and Schwarz, while indicating the 

 local significance of the adopted subdivisions, draw attention to the 

 limited value of this nomenclature, and mention facts which clearly 

 show the contemporaneous variation of facies in the series. Thus, 

 to the north of Uitenhage, the Marine Beds appear to be synchronous 

 with part of the local conglomerate of " Enon " character, and it is 

 pointed out that at Plettenberg's Bay also, the Sunday's Eiver Beds 

 are partly replaced by conglomerate resembling that of the Enon 

 Beds, but here yielding Trigonia conocardiiformis, one of the most 

 characteristic fossils of the Marine Beds.* 



The question of the age to be assigned to the Uitenhage Series, as 

 is well known, has called forth strikingly different opinions from 

 various authors. It was suggested by Stow in 1871 t that the want 

 of unanimity among the earlier writers might have been due to care- 

 less collecting and the mingling of specimens obtained from different 

 horizons. This author therefore made his own collections with due 

 regard to the localities and the individual bands in w r hich he found 

 the fossils to occur, and he attempted a correlation of the fossiliferous 

 beds exposed in sections at various places on the Sunday's and 

 Zwartkop's Eivers. It appears highly probable, however, from the 

 palaeontological evidence alone, that no very considerable extent of 

 time is represented by the w r hole of the beds which yield marine 

 fossils, and there is nothing to show that the different opinions 

 respecting the age of the series have been arrived at in consequence 

 of any radical change in the character of the fauna itself in its dis- 

 tribution through the strata. That any such marked change can be 



* Schwarz (1), pp. 53, 61 ; Kogers and Schwarz (1), p. 5 ; Eogers (1), pp. 282- 

 296. See also Eogers (2), pp. 13, 15. 

 t Stow (1). 



