It might well appear that the labours of Kowalevsky and Filhol had so completely determined the structure of this genus, that nothing of importance remained to add to their results; but this is very far from being the case. The European material, found principally at Hempstead and at Konzon, near PuyinFrance, is so scattered that its proper association is a matter of great difficulty, and errors are unavoidable.

Mr. J. B. Hatcher, AssistantinGeology, and one of the Curators of this Museum, has during the past two summers been engagedincollecting from the Oligocene beds of South Dakota, and among many other treasures has obtained several all but complete skeletons of Ancodus, belonging to the species which Osborn and Wortman have lately named A. (Hyopotamus) brachyrhynchus. This material proves to be of great interest and importance, and will be fully described in an illustrated monograph which is soon to appear. The object of the present preliminary notice is to call attention to some of the more striking characteristics of this curious animal.

The American species of Ancodus present certain constant differences from the European members of the genus. (1) The muzzle is not drawn out into such an extraordinary rostrum; (2) The skull has greater vertical height, though this difference may be due in part to the crushing which the Ronzon specimens have undergone; (3) The coronoid process of the lower jaw is much more prominent and more decidedly recurved.