. The American diceratheres. Rhinoceroses, Fossil; Paleontology. PETERSON: THE AMERICAN DICERATHERES. 403 fessor Loomis. Among Professor Osborn's third phylum of the later Miocene Rhinoceroses"' we may find a representative of this phylum. In Europe Diceratherium pleuroceros (Duvernoy) is the most completely preserved type from the Aquitanian. Its geological horizon apparently approxi- mates in age the John Day beds of North America. From the cast of this European species (Fig. 1) it is seen that the cranium back of the orbit is very suggestive of D. annectens. The brain-case has similar
. The American diceratheres. Rhinoceroses, Fossil; Paleontology. PETERSON: THE AMERICAN DICERATHERES. 403 fessor Loomis. Among Professor Osborn's third phylum of the later Miocene Rhinoceroses"' we may find a representative of this phylum. In Europe Diceratherium pleuroceros (Duvernoy) is the most completely preserved type from the Aquitanian. Its geological horizon apparently approxi- mates in age the John Day beds of North America. From the cast of this European species (Fig. 1) it is seen that the cranium back of the orbit is very suggestive of D. annectens. The brain-case has similar small. Fig. 1. Diceratherium pleuroceros (Duvernoy). From a plaster replica in the Carnegie Museum. X 1/6. proportions, the supra-orbital ridges converge gently to form a similarly short sagittal crest, though less prominent and more rounded in the European form. The inion is also somewhat higher in the latter. The muzzle is long, though higher, and perhaps having more the proportions of that part in D. niobrarense from the Nebraska Miocene. The basi-cranium in the cast of D. pleuroceros is short and the mastoid process is in touch with the post-glenoid process. Thus the contour of the skull of the European species apparently has combined char- acters of D. annectens from the John Day and of D. niobrarense from the Nebraska Miocene. The dentition of the European form is too much worn to allow accurate comparison. By regarding such forms as Protaceratherium* {"Diceratherium^') minutum (Cuvier) of the Stampian as approximately parallel to Coenopus of the upper and middle Oligocene of North America, it appears that the family may be traced back to nearly the same geologic time in Europe and North America,^ ' Bull. Amer. Mus., Vol. XX, 1904, p. 321; {1 Peraceras) planiceps, p. 322; Aphelops {?Diceratherium) brachyodus p. 324. * Abel, 0., "Kritische Untersuchungen iiber die palaogenen Rhinocerotiden Europas," Abh. der K. K. Geologischen Reichsanstalt, Band
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