43 



ACERATHERIUM MITE, Cope. 



Plate IV, fig. 5. 



Aceratherium mitt, Cope, 1874. Annual Report U. S. Geol. and Geog. Survey Terrs, for 

 1873, p. 493. 



Aceratherium mite, Cope, 1885. The White Eiver beds of Swift-current river, North West 

 Territory, American Naturalist, vol. XIX, p. 163. 



Aceratherium mite, Cope, 1885. Geol. and Nat. Hist. Survey of Canada, vol. I, new series, 

 part C, appendix I, p. 83. 



Ccenopus mitis, Cope, 1891. The species from the Oligocene or Lower Miocene beds of the 

 Cypress hills, Geol. Survey of Canada, Contr. to Can. Palceont, vol. Ill (quarto), pt. I, p. 

 19, pi. IV, fig. 2. 



Ccenopus pumilus, Cope, in part, 1891. Idem, p. 19, specimen No. 1, pi. IV, figs. 3, 3a. 



Aceratherium mile, Osborn, 1898. The Extinct Rhinoceroses, Memoirs Amer. Mus. Nat. 

 Hist., vol. I, pt. Ill, p. 136. 



In his 1891 report Cope assigned certain remains of Aceratheres from the Cypress hills 

 to this species. They consist of parts of two left mandibular rami, and are referred to as 

 specimens Nos. 1 and 2. The first specimen is a section of a left ramu3 holding the roots of 

 the last two molars, and extending back beneath the base of the coronoid ; the fragment is 

 87 mm. long. The second is part of the anterior half of another left ramus, with premolars 

 3 and 4 preserved, the roots of premolar 2, and the inner end of the alveolus of a procumbent 

 canine. A figure was given (pi. IV, fig. 2, pt. I of this volume) of this second specimen 

 viewed from above. 



A symphysis of a mandible, also from the Cypress hills, described and figured by Cope 

 in 1891, under the name Ccenopus pumilus, in the same publication as the above, is regarded 

 by Osborn (op. cit. 1898) as properly referable to A. mite. The second of the two specimens 

 on which C. pumilus was founded (pt. I, this volume, pi. IV, fig. 4) has been shown by Pro- 

 fessor Osborn (op. cit. 1898) to be part of the lower jaw of Hyracodon nebrascensis. 



In the type ramus from Colorado, described by Cope in 1874, the space occupied by the 

 first three lower premolars (2, 3 and 4) is 80 mm. as given in the original description. A 

 similar measurement, taken from the "type lower jaw" (and therefore presumably from the 

 same specimen), is stated by Osborn (op. cit. p. 139) to be 55 mm. In specimen 2 from the 

 Cypress hills (A. mite) the three premolars together measure in length 58 mm, and in the 

 symphysial specimen (C. pumilus) a like measurement gives 43 mm. In one only of the 

 three Cypress Hills specimens referred to A. mite, are premolar crowns preserved, and in the 

 type ramus the crowns of the three premolars are imperfect. 



A very perfect lower jaw from the Protoceras beds of South Dakota is referred doubt- 

 fully by Osborn (op. cit. p. 139) to this species. The premolar series in this last specimen 

 occupies a space of 47 mm. 



An upper left third molar tooth, obtained by T. C. Weston at the Cypress Hills locality 

 in 1884, is probably referable to this species. Its dimensions are : — antero-posterior diameter, 

 25 mm., transverse diameter 28 mm. 



