The Invertebrate Fauna of the Uitenhage Series. 37 



and characteristic Uitenhage shell is Exoyyra imbricata Krauss, and 

 this belongs to a general type well exemplified in the Lower 

 Cretaceous strata of Europe and South America. Lima neglecta 

 Tate, belongs to the sub-generic division Mantellum, and most 

 closely resembles forms which occur in the Lower Cretaceous of 

 Europe. Eeference has already been made to Ptychomya complicata 

 (Tate), which is a typical representative of a genus widely dis- 

 tributed in the Lower Cretaceous rocks, where it first makes its 

 appearance. 



It is abundantly evident, then, that many of the most important 

 and distinctive molluscan forms, amongst those with which we are 

 dealing, give similar indications of geological horizon. There can 

 be no doubt, indeed, that the marine Uitenhage fauna is of Neocomian 

 age, though it is perhaps not possible to arrive at a very precise and 

 positive estimate of equivalence with the divisions of the Neocomian 

 in Europe, owing to the want of close coincidence in the faunas as 

 developed in such widely separated regions. But Holcostephanus 

 atherstoni (Sharpe) and H. wilmance, sp. nov., if not actually repre- 

 sented in Europe, have very close allies there in the Valanginian 

 and Hauterivian, and the Uitenhage Marine Beds may, in my 

 opinion, be certainly correlated with these divisions. Further, it 

 seems to me highly probable that the Marine Beds represent not 

 more than the strata at the top of the Valanginian and the base of 

 the Hauterivian. 



The possibility that the lowest marine strata may be of greater 

 age than Neocomian is not only most remote, but is contradicted 

 by the palaeontological evidence, so far as this goes. Fossiliferous 

 strata, yielding a marine molluscan fauna characterised by the 

 prevalence of Gasteropoda and the remains of oysters, occur at 

 Dunbrodie (Sunday's Eiver) associated with plant-bearing beds, and 

 are in the lower part of the Uitenhage Series ; according to Messrs. 

 Eogers and Schwarz they may be classed with the so-called "Wood 

 Bed " series. Amongst the fossils collected here are Actceonina 

 atherstoni (Sharpe), Cyprina rugulosa Sharpe, and a Pecten which 

 I have identified as Pecten cottaldinus d'Orb. While Actceonina 

 atlierstoni is found also in the highest part of the Marine Beds 

 on the Zwartkop's Eiver and with the characteristic TrigonicB on the 

 Sunday's Eiver, Stow recorded the occurrence of Cyprina rugulosa 

 with similar associates. Although the Wood Bed series was not 

 seen in the Zwartkop's Eiver Valley below Uitenhage, the lowest 

 part of the Marine Beds in the Zwartkop's Eiver section, exposed 

 in a clay-pit near Eawson Bridge, yielded Actceonina atherstoni and 



4 



