7-4 



CENOZOIC MAMMAL HORIZONS 



tion contains, among Oreodontidse, Pr ornery cochcerus {P. vantassel- 

 ensis), PJienacoccdus (P. typus ), also a primitive brachyodont stage 

 of Merychyus; among Camelidse, two brachyodont genera, namely, 

 Miolabis and a related form, Oxydactylus; Stenomylus, a cameloid 

 of the Hypisodus type;'' among Hypertragulidse, Syndyocems,^ wliich 

 replaces Protoceras (of the upper Brule level); among Dicotylidse, 

 primitive species of Desmathyus; among Rodentia-Castoridse, Ste- 

 neofiber, very abundant (2 sp.); among Equidse, Parahippus; among 

 Mustelid^e, Brachypsalis. 



(d) Harrison formation, Agate Spring quarry. — Near the middle 

 of the Harrison formation is the extraordinarily rich deposit of this 

 quarry, which gives us a nearly if not quite complete picture of the 

 larger mammals of this region and period. So far as described by 

 Peterson/ it contains, among Perissodactyla-Equidae, Parahippus; 

 among Rhinocerotidae, Diceratherium, 2 species; among Chalico- 

 theriidse, Moropus; among Artiodactyla-Oreodontidse, Merychyus and 

 Mery cochcerus; among Elotheriidse, Dinohyus, a giant form similar 

 to the large John Day types and probably the last of its family; 

 among Carnivora-Canidae, Nothocyon, Amphicyon (a very primitive 

 form, its earliest appearance in America). 



B. UPPER DIVISION. 



{e) Upper part of Harrison formation."^ — Among Artiodactyla- 

 Oreodontidse, Merycochosrus (first abundant appearance of this 

 genus), Merychyus; among Camelidse, "^.Miolabis and Oxydactylus, 2 

 species; the first appearance of the family Cervidse, genus Blastomeryx, 

 a modernized selenodont artiodactyl; Dicotylidse, Desmatliyus; 

 among Perissodactyla-Equidae, Parahippus, a large brachyodont horse 

 constituting the most abundant type and most characteristic stage; 

 among Chalicotheriidse, Moropus; among Carnivora-Mustelidae, ^lu- 

 rocyon. Also 2 species of Testudo. 



EASTERLY SECTION. 

 (Fig. 12.) 



About 90 miles farther east along Pine Ridge in northern Nebraska 

 and on the south side of White River is the formation, also overly- 

 ing the upper Brule clay, named by Matthew and Gidley ^ (1904) the 

 Rosebud beds. This is the region of the typical Arikaree section of 

 Darton, described and named in 1899. The section (fig. 12) was 

 made by Albert Thomson, of the American Museum expedition of 1906. 



a Peterson, op. cit. 



b Barbour, E. H., Notice of a new fossil mammal from Sioux County, Nebr. : Nebraska Geol. Sur- 

 vey, vol. 2, pt. 3. 



c The Miocene beds of western Nebraska, etc.: Ann. Carnegie Mus.. vol. 4. 1906, pp. 21-72. 



d Erroneously termed "Nebraska" in Peterson's first report. The Agate Spring fossil quarry: 

 Annr Carnegie Mus., vol. 3. 1906, p. 487. 



f New or little knowTi mammals from the Miocene of South Dakota: Bull. Xm. Mus. Nat. Hist., vol. 

 20, 1904, pp. 241-268. 



