The fossil remains described and discussed in this paper were taken from about the middle of the Karroo Beds near Tanga, on the coast of the Tanganyika Territory, by Mr. F. P. Mennell, F.G.S., who was good enough to forward the specimens to me for examination. They consist of portions of three animals, of which one is too weathered and too fragmentary for investigation. The other two are preserved on slabs of hard, blackish, somewhat micaceous shale; the more complete animal is smaller than the other, but, as will be seen in the sequel, in other respects they are sufficiently similar to be considered representatives of the same species.