FROM TANGANYIKA AND KENYA 5 



Mr. C. P. Palmer, of the same Department, has rendered invaluable assistance with 

 the preparation of many of the fossil illustrations. 



II HISTORY OF INVESTIGATION OF JURASSIC MOLLUSCA OF EAST AFRICA 



Knowledge of the Jurassic stratigraphy and palaeontology of East Africa has 

 been reviewed at rather frequent intervals as it has progressed during the past 

 hundred years. Successive works which may be particularly mentioned in this 

 connection are those of Neumayr (1885), Dacque & Krenkel (1909), Behrend (1918), 

 Krenkel (1925), Arkell (1956), Aitken {in Quennell et at., 1956 ; also in Quennell 

 et al., 1957), and Pulfrey (1963). In view of the existence of these works, particularly 

 the later ones, it is necessary for the purposes of the present memoir to do little 

 more than summarize the history of the study of the Jurassic bivalves and gastro- 

 pods of the region, although a few passing references may be made to work on the 

 ammonites. 



The earliest record of the occurrence of marine Jurassic rocks in East Africa was a 

 short note by Fraas (1859) recording the discovery by a missionary, J. L. Krapf, of 

 an ammonite at Kisaludini, near Mombasa. This specimen, originally identified 

 as Ammonites annularis Reinecke, was subsequently described as Perisphinctes 

 (Virgatosphinctes) krapfi by Dacque (1910 : 13, pi. 3, fig. 3), who showed that its age 

 was Upper Oxfordian and not Upper Dogger (Callovian), as supposed by Fraas. 



Beyrich (1877, 1878) published two short papers on ammonites which the ex- 

 plorer J. M. Hildebrandt had sent to him from localities near Mombasa, his con- 

 clusion being that various stages of the Jurassic are represented in the district. In 

 the account of his journey Hildebrandt (1879 : 2 54> 2 7 2 ) mentioned the occurrences 

 of Jurassic beds in the district. Further south, in Usambara, the northern coastal 

 district of Tanganyika, fossiliferous rocks now known to belong to the Jurassic were 

 recorded by the English traveller J. Thomson (1879, 1881), but he thought that their 

 fossils suggested a Carboniferous age. Farler (1879 : 87) referred to the occurrence 

 of a fossiliferous pisolitic limestone in the same area but made no suggestion regard- 

 ing its age. 



Baumann (1891 : 4, 116), in his work on Usambara, definitely recorded the pre- 

 sence of Jurassic rocks in that area but cited none of the included fossils by name, 

 and in the same year Stuhlmann (1891) referred to the outcrop of a narrow belt of 

 Jurassic rocks behind the Tertiary formations near Pangani, further south, mention- 

 ing that they contained ammonites. A number of fossils, mostly ammonites, 

 collected by Stuhlmann at the locality Mtaru were described by Tornquist (1893), 

 who assigned an Oxfordian age to them ; no bivalves or gastropods were mentioned. 

 In the same year, Jaekel (1893) published a short note on some Jurassic fossils from 

 Usambara sent to Germany by G. Lieder, by then established as official geologist in 

 what was at that time German East Africa. For the first time reference was made 

 to some Bivalvia, including an oyster said to be scarcely separable from Ostrea 

 dextrorsum Quenstedt (a probable synonym of Lopha solitaria (J. de C. Sowerby)), 

 a Lima and a PseudomonotisH , neither identified specifically. An Upper Jurassic 

 age was assigned to these forms. In the next year Stuhlmann himself (1894a, b) 



