APPENDIX. 



Art. XYIII. — Restoration of Brontops robustus, from the 



Miocene of America ; * by Professor 0. C. Marsh. (With 



Plate VI.) 



f 



The largest mammals of the American Miocene were the 

 huge Brontotheridce, which lived in great numbers on' the east- 

 ern flanks of the Pocky Mountains, and were entombed in the 

 fresh-water lakes of that region. They were larger than the 

 Dinocerata of the Eocene, and nearly equalled in size the ex- 

 isting elephant. They constitute a distinct family of perisso- 

 dactyles, and were more nearly allied to the rhinoceros than to 

 any other living forms. 



The deposits in which their remains are found have been 

 called by the author, the Brontotherium beds. They form a 

 well-marked horizon at the base of the Miocene. These deposits 

 are several hundred feet in thickness, and may be separated 

 into different subdivisions, each marked by distinct genera or 

 species of these gigantic mammals. 



The author has made extensive explorations of these Miocene 

 lake-basins, and has secured the remains of several hundred 

 individuals of the Brontothericlce, which will be fully described 

 in a monograph, now well advanced towards completion, to be 

 published by the United States Geological Survey. The atlas 

 of sixty lithographic plates is already printed, and the author 

 submitted a copy to the section. The last plate of this volume 

 is devoted to a restoration of Brontops robustus, one-seventh 

 natural size, and a diagram enlarged from this plate to natural 

 size was also exhibited, f 



* Abstract of a paper read before Section D, of the British Association for the 

 Advancement of Science, at the Bath meeting, Sept. 7th, 1888. 



f The present plate (VI), one twenty -fourth natural size, shows a reduced copy of 

 the same restoration. 



