Physician and distinguished South African paleontologist and Elliot Gold Medalist of the U. S. National Academy of Sciences. He occupied the chair of geology and zoology at Victoria College, Stellenbosch and later was appointed to a post in the Transvaal Museum. He was chiefly known for his studies on mammal-like reptiles. This letter addressed to C. M. B. Cadwalader, explains his theories on certail fossils. Illustrated with pen and ink sketches.