152 Annals of the Carnegie Museum. 



massen mit sich fiihren. Wir wissen von Wiisten- und Step{)entieren, 

 dass sie solchen Naturereignissen gegeniiber sich so verhalten, als 

 waren sie sich der ihnen drohenden Gefahr bewusst, und dass sie ihr 

 gegeniiber das ihnen angeborene, passive Verteidigungsmittel des 

 Sichzusaniniendrangens in Anwendung bringen. Dies haben offenbar 

 auch unsere drei Exemplare von Promerycocluvnis getan." 



These skeletons were evidently buried quite rapidly, but not so 

 rapidly as to remain completely articulated, as the caudal vertebrae 

 are mostly gone, perhaps carried off by carnivora. If the skeletons 

 had been completely covered up by the supposed storm in which they 

 perished, the abdominal cavity would soon have given w-ay to the 

 impact of the sand, leaving the backbones more nearly in position, 

 and the caudals would most likely also have been present. It is seen 

 that the posterior portions of the dorsal regions are dislocated and 

 have dropped to a lower level than the remainder of the vertebral 

 column. This would indicate, that after the storm in which the animals 

 perished, the backbones were exposed long enough for the muscles 

 and ligaments to rot off, and thus the vertebrae with less completely 

 interlocked zygapophyses or other supports dropped down out of their 

 original positions before the ground had been raised high enough to 

 support them in place. The position of the group together with the 

 condition of the sediment, an imperfectly stratified mass, adds strength 

 to the theory of the fluviatile and seolian origin of the deposits in 

 this locality, advocated by Matthew, Hatcher, and others.^ The 

 habitat of these animals was undoubtedly a sandy region, permeated 

 by rivers, lakes, lagoons, and marshes. 



Narrative of the Discovery of the Group of Skeletons 

 Representing Promerycochcerus Carrikeri. 



It is seldom in the history of mammalian paleontology that a 

 species has been established on more complete material than the one 

 discussed in the following pages While collecting fossils for the Car- 

 negie Museum in 1901 on Badland Creek, Sioux County, Nebraska, 

 the writer became acquainted w-ith two young men, Messrs. M. A. 

 Carriker, Jr., and M. Carry, then students in the Nebraska State 

 University, who were collecting recent birds and mammals in the 

 same neighborhood. Mr. Carriker, who was interested in some 



* See the recent paper in the Bull. Geol. Soc. America, Vol. XXII, 191 1, p. 687- 

 714, by C. R. Keyes. 



