Lamellibranchia from the Karroo Beds of the Ruhuhu Coalfields, Tanganyika Territory

Publisher Website
Google Scholar
Abstract
I. I ntroduction T his paper describes an interesting series of Karroo lamelli-branchs collected by Mr. G. M. Stockley during his recent survey of the Ruhuhu coalfields, east of Lake Nyasa. These fossils come from two distinct horizons, the lower belonging to the upper part of the Ruhuhu Beds, which overlie the local Upper Coal-Measures, and the upper to the Manda Beds, near the top of the Karroo System, as developed in this district. The Ruhuhu Beds, which consist largely of fine-grained calcareous sandstones and shales, are overlain by the Lower Bone Bed (of Stockley), which contains reptilian remains determined by Dr. S. H. Haughton as belonging to a middle Lower Beaufort horizon. The lamellibranch fossils now described, which are very abundant in certain beds, are small freshwater shells referable to five species of the genus Palœomutela , two of which occur in South Africa, and one, P. oblonga (Jones), in Nyasaland. Wherever Palœomutela and the allied genus Palœanodonta have been found in Karroo beds, they always seem to occur at a Lower Beaufort horizon, and it is rather remarkable that they have not yet been found in the underlying coal-bearing beds of the Ecca stage. In view of this restricted range, it is most probable that the molluscan horizons of the Ruhuhu Beds, like the overlying Lower Bone Bed, are of Lower Beaufort (that is, uppermost Permian) age. The most important work on these Karroo lamellibranchs is a paper by Amalitsky (1895) ,1 who shows that most of the