during life is demonstrated by the large callus growths on the broken ends, but the pieces did not knit. [Illustration: FIG. 194.—Specimen showing characteristic grooves of wear in the anterior teeth of †entelodont (_†Archæotherium_) from upper White River beds. Princeton University Museum.] In the middle and lower substages of the White River the genus (_†Archæotherium_) was the same as in the upper substage of these beds, but the species were all smaller and some of them very much so, not exceeding an ordinary pig in size. Throughout the series, as we now have it, from the lower Oligocene into the lower Miocene, there is very little change except in size, all the essential features of structure remaining the same; the genera are therefore distinguished by modifications of very secondary importance, and it is a question whether all the species should not be included in a single genus. The European genus _†Entelodon_, which gives its name to the family, is so like the American forms that by most writers the White River species are referred to it. It is of interest to note that the †giant pigs have also been found in the marine Miocene of New Jersey, one of the few records of the Tertiary land mammals of the Atlantic seaboard. At present, the †entelodonts proper cannot be traced back of the lower White River beds, nor are they found in any more ancient formations in Europe. It is, therefore, probable that they were immigrants in both of these continents, presumably from Asia. [Illustration: FIG. 195.—Skull of †short-faced pig (_†Achænodon robustus_) from the Bridger Eocene. Princeton University Museum.]