OLIGOCENE OF EUROPE, NORTH AFRICA, AND NORTH AMERICA 235 



gigantic plant (Barbour, 1897 ^) ; then as the burrows of the castorid rodent 

 Steneojiber, remains of which were found to occur inside (Peterson, 1905) ^; 

 more recently Riggs •* has reported skeletons of other animals drawn to- 

 gether within these spirals, a fact which tends to throw doubt upon the 

 rodent 'burrow theory.' 



Near the summit of the Lower Harrison stream bed formation is the 

 extraordinarily rich deposit known as the Agate Spring Quarry, thoroughly 



Fig. 119. — View of the Dsemonelix beds near Harrison, Sioux County, Nebraska, showing 

 the problematical DcEinonclix, or "devil's corkscrews." From the Morrill Collection of Geo- 

 logical Photographs, University of Nebraska, by permission of E. H. Barbour. 



explored by Barbour of the University of Nebraska and by Peterson for the 

 Carnegie Museum, and yielding a nearly if not complete picture of the 

 larger mammals of this region and period. Here has been found especially 

 a complete skeleton of the giant chalicothere Moropus and of the giant 

 entelodont Dinohyus, and smaller forms of Diceratherium in great abundance. 

 This quarry was first reported by James H. Cook about 1890 in the center 

 of a region rich in fossils. 



The mammals of this period have been chiefly described by Barliour, 

 Peterson (1906), and Matthew.* The last author, in describing (1907) the 



* Barbour, E. H., On a New Order of Gigantic Fossils. Nebr. Univ. Stud., Vol. I, no. 4, 

 July, 1892; and Nature, Structure and Phylogeny of Dcemonelix. Bull. Gcol. Soc. Amir., Vol. 

 VIII, April, 1897, pp. 305-814. 



2 Peterson, O. A., Description of New Rodents and Discussion of the Origin of Dwinonelix. 

 Carnegie Mua. Mem., Vol. II, 190.'), pp. 1.39-191. 



' Riggs, Remarks on Dwmoneli.v, Ainer. Soc. Vertebr. Pal., 7th. Ann. Meet., Baltimore, 

 Dec. 1908. 



^ Principal titles are given in Bibliography. 



