IV. On a newly discovered extinct Mammal from Patagonia ( Homalodotherium Cunninghami )

The author describes the complete adult dentition of a new genus of mammal, founded on remains discovered by Dr. Robert O. Cunningham in deposits of uncertain age on the banks of the River Gallegos, South Patagonia. The animal appears to have possessed the complete typical number of teeth,i. e . twenty-two above and below, arranged in an unbroken series, and of nearly even height, and presenting a remarkable gradual transition in characters, in both jaws, from the first incisor to the last molar. The molars more nearly resemble those of the genusRhinoceros than any other known mammal; and, judging only by the general characters of the teeth, the animal would appear to have been a very generalized type of Perissodactyle Ungulate, allied throughHyracodon (a North-American Miocene form) toRhinoceros , also more remotely toMacrauchenia , and, though still more remotely, to the aberrantNesodon andToxodon . The generic nameHomadodotherium was suggested for this form by Professor Huxley in his Presidential Address to the Geological Society in 1870.