4 JURASSIC BIVALVIA AND GASTROPODA 



1 INTRODUCTION 



During the past 40 years numerous fossil invertebrates from the Jurassic rocks of 

 East Africa have been added to the collections of the British Museum (Natural 

 History). This material has come from several sources. From 1924 to early in 

 1931 the Museum sent a series of expeditions to collect from the dinosaur beds of 

 Tendaguru, Tanganyika, under the leadership of W. E. Cutler, J. Parkinson and 

 F. W. H. Migeod in succession, and the material brought back to England included 

 many invertebrate specimens as well as dinosaur bones. From about the same 

 period to the present day the Geological Survey Departments of Tanganyika and 

 Kenya have from time to time sent collections of fossils to London for identification, 

 and the material from these sources which has been deposited in the Museum during 

 the past few years has been particularly extensive. From 1951 to 1959 the B.P.- 

 Shell Petroleum Development Company of Tanganyika Ltd. investigated a con- 

 siderable area of the coastal region of the two territories and a selection from the 

 Jurassic specimens collected has been generously presented to the Museum. Small 

 collections from East Africa have also been acquired by the Museum from other 

 sources. Preliminary reports on some of the Geological Survey material have 

 appeared in the publications of these institutions, and in a few cases these have 

 included illustrations of some of the fossils. Otherwise, the only publications 

 dealing with Jurassic bivalves and gastropods from this region now in the Museum 

 consist of two short notes by the present writer (Cox, 1937a, 1937&). It has, there- 

 fore, now seemed appropriate to describe in a single memoir all the East African 

 Jurassic material belonging to these classes which is now available in London. 



This account has been written at a time when there are movements afoot to 

 stabilize Jurassic stratigraphical nomenclature by international agreement. It 

 seems probable that the decision may be reached to restrict the range of the Kim- 

 meridgian stage in accordance with non-British usage, and possible that the term 

 Portlandian may be abandoned. It is, however, uncertain what stage name (Vol- 

 gian or Tithonian) will be accepted for Jurassic beds of later date than the restricted 

 Kimmeridgian. In East Africa ammonite evidence establishes the age of the pre- 

 Cretaceous marine beds at Tendaguru as Upper Kimmeridgian in the British sense 

 (Arkell 1956 : 355), and there is no palaeontological evidence for correlating any 

 deposits with the type Portlandian or with post-Kimmeridgian (sensu anglico) 

 horizons of the European Tithonian. It has therefore been decided to use the term 

 Kimmeridgian in the British sense in the present memoir, to dispense with the 

 terms Portlandian and Tithonian, and merely to allude to very late Jurassic beds, 

 the exact age of which is unestablished, as " uppermost Jurassic ". 



The writer expresses his great indebtedness to all who have placed specimens and 

 information at his disposal, particularly successive Directors and members of the 

 staffs of the Tanganyika and Kenya Geological Surveys, and Dr. F. E. Eames and 

 his colleagues of the palaeontological staff of the British Petroleum Company, Ltd. 

 Mr. D. L. F. Sealy, of the Department of Palaeontology of the British Museum 

 (Natural History), has drawn the two sketch-maps appearing as text-figures, and 



