"Annular mounds of clinkery lava encircling shallow depressions floored with similar lava were recently discovered by the late A. D. Combe in S. W. Uganda. From their morphological, petrographic, and chemical peculiarities, here described, it is inferred that they represent transfusion products of superficial tuff occupying the sites of unusually hot fumaroles. The dominant added materials are found to be iron oxides, TiO 2 , K 2 O, and P 2 O 5 . It is suggested that the P 2 O 5 , which is abnormally abundant, may have been derived from bone beds in the underlying Kaiso series."

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