Ungulata

Artiodactyla.

This order is chiefly dealt with in the article ARTIODACTYLA. Here it may be noted that attempts, as by Cope and others, to brigade the artiodactyls with the perissodactyls under the terms Taxeopoda or Ungulata Vera have in the long run only served to bring out the entirely artificial nature of such an assemblage and to throw into relief the significant differences which widely separated these two orders from each other as far back as Lower Eocene times. There is indeed more to be said in favour of the view that the Artiodactyla may be an offshoot of some forerunner of the mesonychid family of the creodonts, while the Perissodactyla may be related remotely to the Cre taceous ancestors of the condylarths. Recent studies by Miss H. S. Pearson on the skull structure of the earliest artiodactyls have revealed that at a very early date the order was already subdivided into two series, one the amastoid series, in which the mastoid region of the periotic bone was completely covered by the squamosal and adjacent elements (as in the suillines and their extinct relatives) and the other, or mastoid series, in which the mastoid was well exposed on the outer side, as in the Eocene Dichobunidae and all the ruminant artiodactyls.

In conclusion, much future palaeontologic exploration, in Africa, in Mongolia and many other parts of Asia, will doubtless be necessary before many of the problems touched upon in this article can be pushed forward nearer to solution.

BIBLIOGRAPHY.—General: W. H. Flower and R. Lydekker, Mammals, Living and Extinct (1891) ; H. F. Osborn, The Age of Mammals (Iwo) ; History:—W. K. Gregory, "The Orders of Mammals," Bull. Amer. Mus. Nat. Hist. (Iwo).

Condylarthra: W. D. Matthew and Walter Granger, "A Revision of the Lower Eocene Wasatch and Wind River Faunas, Part III.,—Order Condylarthra," Bull. Amer. Mus. Nat. Hist. (1915).

Dinocerata: 0. C. Marsh, "Dinocerata," U.S. Geol. Surv. (1884)• Extinct South American Ungulates: W. D. Scott, Rept. Princeton Univ. Exped. Patagonia, 1896-1899, Vol. VII., Palaeontology (1910 12) ; W. J. Sinclair, Rept. Princeton Univ. Exped. Patagonia, 1896 1899, Vol. VI., Palaeontology (19o9).

Hyracoidea, Embrithopoda, Barypoda: C. W. Andrews, "Catalogue of the Tertiary Vertebrata of Fayam, Egypt," Mem. Brit. Mus. (Nat. Hist.) (1906).

Proboscidea: C. W. Andrews, "Catalogue of the Tertiary Vertebrata of Fayilm, Egypt," Mem. Brit. Mus. (Nat. Hist.) (1906) ; H. F. Osborn, "Mastodons and Mammoths of North America," Nat. Hist. (1923) ; Monograph (in preparation) and numerous papers on "Pro boscidea," Bull. Amer. Mus. Nat. Hist. (1907-1928).

Sirenia: C. Deperet and F. Roman, Le Felsinotherium Serresi (Lyon, 192o). (W. K. G.)