M JURASSIC BIVALVIA AND GASTROPODA 



Vietteia mandaivaensis sp. nov. 

 Pietteia stockleyi sp. nov. 

 Pictavia tanganyicensis sp. nov. 

 Ampullospira besairiei sp. nov. 



All except four of the species in the above list are new, and not one occurs in rocks 

 regarded as Bajocian in S.E. Kenya or in the Kidugallo district of Tanganyika. 

 Hennig (1917), however, recorded Gervillia aff. iraonensis Newton from the Pindiro 

 Shales and the species in question, Bakevellia iraonensis, is here recorded from Bajo- 

 cian beds at Ngerengere, west of Kidugallo. The four previously described species 

 in the above list from the Pindiro Shales include Pinnabuchii, Thracia lens and Modio- 

 lus imbricatus, all of which occur in Europe in both the Bajocian and the Bathonian, 

 the third (as in East Africa also) ranging up into much later beds. The fourth 

 species, Gervillella orientalis, was originally described from the Moghara massif of 

 Sinai, where it is known from later collecting to occur in beds of undoubtedly 

 Bathonian age. On the other hand, one of the species of the Pindiro Shales now 

 described as new, Ampullospira besairiei, occurs in beds in Madagascar known to be 

 Bajocian in age. It would thus appear that the palaeontological evidence as to 

 whether the Pindiro Shales should be referred to the Bajocian or to the Bathonian 

 is still inconclusive. 



Bathonian Assemblages 



Uncertainty about exact delimitation of Bathonian beds from those of earlier and 

 later stages exists throughout East Africa (cf. Aitken 1961 : 17-19), and none of 

 the Mollusca from Tanganyika here described can be unhesitatingly referred to this 

 stage. It is, however, probable that specimens of Liostrea dubiensis (Contejean) 

 from 1 mile and 2 miles west of Magindu Station, on the Tanganyika Central Rail- 

 way, are from the Bathonian. In the Rahmu area of N.E. Kenya the Murri Lime- 

 stones of Thompson & Dodson (1958 : 15) are considered to be largely or entirely 

 Bathonian in age, and have yielded the three species Brachidontes (Arcomytilns) 

 aspcr (J. Sowerby), Chlamys curvivarians (Dietrich) and Lima (Plagiostoma) biinien- 

 sis sp. nov., as recorded in the present memoir. Further species from those lime- 

 stones have been recorded by Weir (1929), and also by Ayers (1952 : 27) on the basis 

 of identifications by J. A. Douglas, and are listed by Thompson & Dodson (1958 : 

 19). Some of the determinations in question, for example, of the Oxfordian species 

 Cercomya siliqua Agassiz and Exogyra fourtaui Stefanini, appear suspect. 



The most interesting assemblage from beds of approximately Bathonian age in 

 N.E. Kenya is that from the Asaharbito Beds of Thompson & Dodson (1958 : 21). 

 Not all the provisional identifications originally cited have been confirmed, and the 

 following revised list from this horizon (omitting forms identified only generically) 

 can now be presented : 



Grammatodon sublaevigatus (Zieten) 



Liostrea dubiensis (Contejean) 



Trigonia cf. brevicostata Kitchin 



Astarte ayersi sp. nov. 



