Karroo Lamellibranchia from Tanganyika Territory and Madagascar

Abstract

This paper deals primarily with a large collection of lamellibranchia obtained by Mr. G. M. Stockley in 1931 from the Karroo beds of the Kidodi district of Tanganyika Territory. These fossils are of considerable interest as affording the first evidence of an Upper Permian marine incursion into an African Karroo basin of deposition, and also include numerous non-marine species new to the Karroo fauna. It would have been impossible to determine the age of the marine fossils with any degree of certainty had it not been for the fortunate coincidence that, while studying them, I was shown a collection, including two of the same species, obtained from a known horizon in Madagascar by Mlle E. Basse. I must express my very warm thanks to her for relinquishing her original intention of describing her material herself and kindly permitting me to figure some of her specimens in the present paper. The following details of the succession in the Kidodi district indicate the horizons of the fossils collected by Mr. Stockley:— Ruhembe Beds (3700 foot).— Sanstones and carbonaceous shales, including two molluscan horizons, the upper marine and the lower freshwater, separated by 1200 feet of massive sandstone. The lower horizon is 250 feet from the base of this series. Calcareous Beds (700–800 feet).—Carbonaceous shales, silicified limestones and calcareous sandstones, including an horizon with non-marine mollusca (mainly Kidodia , gen. nov.) about 415 feet from the top. Ndeke Beds (2900 feet).—Sandstones and conglomerates with intercalated mudstones, etc. Unfossiliferous. The rocks belonging to the upper