FROM TANGANYIKA AND KENYA 49 



Oxfordian or Kimmeridgian. 17 miles S. of Rahmu, N.E. Kenya ; Upper Oxford- 

 ian, Seir Limestones. Several localities around Tendaguru, Tanganyika ; Upper 

 Kimmeridgian, " Trigonia smeei " and Nerinella Beds. Kinjele, 5 miles W. of 

 Mtapaia, N. of Tendaguru, Tanganyika ; Upper Kimmeridgian, Indogrammatodon 

 Bed. 



Remarks. Hennig and Dietrich did not adopt Miiller's specific name lieberti, the 

 first to be applied to East African specimens of this species, when recording speci- 

 mens from Tendaguru, because Miiller's description and figures suggested that he 

 was dealing with a form in which the shell was completely smooth. The material 

 from this locality now studied, however, includes specimens which appear smooth 

 either because their outer shell layer has disappeared or because they are merely 

 internal moulds. It thus seems evident that Miiller's types were specimens pre- 

 served in one of these ways. Hennig apparently overlooked Krenkel's description 

 of Avicula tschingira when founding his species Pseudomonotis tendagurensis. 



In specimens from the Tendaguru district the left valve is ornamented with 

 numerous closely arranged, narrow, round-topped riblets of unequal strength, 

 increasing by intercalation. Details vary considerably in different shells. On parts 

 of the surface in many specimens the riblets alternate in strength or weaker ones 

 alternate with pairs of stronger ones. On some specimens the stronger ribs bear 

 obscure, evenly spaced, imbricating scales. Right valves are of feeble convexity 

 and bear well separated radial riblets. It has seemed important to reach a decision 

 as to the identity of the Meleagrinella which is the most abundant species found in 

 the Golberobe Beds of northern Kenya, and has been figured by Saggerson & Miller 

 (1957 : 19, figs. b-d). I am now convinced that it is not possible to draw any specific 

 distinction between this form and the Tendaguru species, as specimens with closely 

 similar ornament occur in both areas. Those now illustrated include one (figs. 3a, b) 

 with particularly numerous and closely spaced ribs. In the Golberobe specimens 

 the right valve is almost smooth, with faint radial ribbing appearing in its later 

 growth-stages. The largest of these specimens are about 15 mm. long. 



It is also necessary to discuss whether previous workers have been justified in 

 asssuming that the Tendaguru species is distinct from any found in Europe. In M. 

 echinata, a European form recorded above from Tanganyika, the left valve is more 

 strongly inflated and the ribs are less numerous, stronger, and more uniform in 

 strength. In M. braamburiensis (Phillips), which occurs in the European Callovian 

 and Oxfordian and has been well figured by Douglas & Arkell (1932 : 163, pi. 12, 

 figs. 5, 6), the ornament is very similar to that of the Tendaguru form, but specimens 

 commonly attain a length of 25-30 mm., which much exceeds the usual size of the 

 latter. The species described by Trautschold as Aucella radiata and discussed in 

 1912 by Sokolov (who has included Avicula tenuicostata Greppin in its synonymy) 

 appears, however, to be indistinguishable from the East African form, as inspection 

 of de Loriol's figures of A . tenuicostata will show. In Europe M. radiata occurs in the 

 Lower Oxfordian, so that its recognition in the Golberobe Beds of Kenya is in keep- 

 ing with the supposed Oxfordian age of these beds. In view of its occurrence at 



