F. B. Loomis — Lthinocerotidce of the Lower Miocene. 51 



Art. IT. — Rhinocerotidm of the Lower Miocene; by Feed- 

 eric B. Loomis. 



Formerly the Lower Miocene beds of America were 

 considered by vertebrate palaeontologists to be practically 

 barren of vertebrate fossils ; but three years ago Mr. Peter- 

 son opened in them the Agate Spring quarries from which 

 have been taken literally hundreds of skulls and disassoci- 

 ated skeletons, among which two species of rhinoceros of the 

 htherto rare genus Diceratherium are far the most abun- 

 dant. In the ''breaks" of the neighboring hills scattered 

 remains have also been found, and it was the fortune of the 

 Amherst '96 expedition, during the summer of 1907, to find a 

 small pocket of rhinoceros bones some 300 yards north of the 

 above mentioned quarries. These latter remains are remark- 

 able in that they represent seven different rhinocerine species 

 all buried together. Four of the species are new and as they 

 represent some unexpected phases^ they are not only described, 

 but a broad study of the whole group in the Lower Miocene 

 is here undertaken. While with the three new species added 

 in this paper, thirteen species of Diceratherium are now 

 known, the genus has never been carefully studied, partly 

 because the early species assigned to it were never figured and 

 were with difficulty accessible. For this paper the Yale 

 Museum has allowed the study of the Marsh material and the 

 figuring of his types, which were but 

 briefly characterized. The following 

 paragraphs will therefore consider the 

 genus Diceratherium, as to its char- 

 acteristics, distribution and the sys- 

 tematic relations of its species. The 

 Aceratheria of the Lower Miocene will 

 also be described, as the genus has not 

 previously been found in the Amer- 

 ican strata later than the Oligocene. 



The genus Diceratherium was estab- 

 lished in 1875 by Marsh for the species Fig.1. Diceratherium nio- 

 D. armatum* its distinctive feature 6'^nse p. / second upper 



. . ' .. „ , molar, one-half nat. size. 



being the presence of a pair ot horn Key to terminology: a, pre- 

 cores on the nasal bones. While the fossette ; &, med. fossette ; 

 animal was rather long-limbed and light c > c f ocnet ; d,metacone; e, 



i m, ^i i i x t ; . • i • n ,i metaconute : /, postfos- 



built, as the skeletal material is mostly sette . g> hypocone ; h, cin- 



disassociated no attempt will here be gulum ; i, protocone ; j, 



made to discuss this part of the skele- f ro J£™™* e ; & ' P aracone : 



ton. The teeth vary considerably, the ' P aiasty e - 



*This Journal, vol. ix, p. 242, 1875. 



