Tooth-Structure — Lamhe. * 243 
reason, the attempt to improve matters with our oils by 
cracking has merely exaggerated the evil, destroying the 
best instead of the worst elements of the oil, and producing 
large quantities of very unstable bodies which have to be 
completely removed by the chemical treatment. It seems 
altogether probable that the bad qualities foujid in Cali- 
fornia kerosene are inherent in the nature of the oil, and 
can not be removed by any possible treatment or manipu- 
lation. 
ON THE TOOTH-STRUCTURE OF MESOHIPPUS WESTONI 
(COPE).* 
By Lawbbncb M. Lambk, F. G. S., F. R. S. C. 
/ 'ertebrale Palaeontologist to the Geological Sitrvey of Canada. 
PIRATE xiv. 
Mesohippus tvestoni was first described by professor 
Ti. D. Cope in the American Naturalist, 1889, p. 153 ( Anchi- 
iJierium^ westoni +) from a right upper molar and two right 
lower molars collected by Mr. T. C. Weston, from the Olig- 
ocene deposits of the Cypress hills, Assiniboia, Canada, in 
1884. The exact locality where these fossil remains were 
discovered is near the eastern end of the Cypress hills in 
Bone coulee at the head waters of Swift Current creek. 
Cope's description appeared later, in the same words, in his 
final memoir,t on the Geological Survey collections from 
the Cypress hills, published in 1891. In 1904 professor H. 
F. Osborn in his paper on "New Oligocenc Horses"§ fur- 
ther characterized the species from a personal examination 
■of the type material. Last summer the writer obtained, at 
the type locality, an additional upper molar that increases 
■our knowledge of the tooth structure of this interesting and 
A^ery primitive species. 
The upper molar described by Cope is imperfect, the 
outer slope of the ectoloph is missing and the anterior bor- 
* Communicated by permission of the Actiner Director of the Geo- 
log'it-al Survey of Canada. 
t See also American Naturalist, 1885, p. 165. Anchithetium sp. indet. 
1 Geological Survey of Canada, Contributions to Canadian Palae- 
•ontolog-y, vol. III. (quarto), part 1, 1891. Anchiterium ivestoni. p. 20, 
pi. xiv, figs. 1, 2, 2a. 
§ Bulletin of the American Museum of Natural History, vol. xx, 
;article xiii, p. 169, 1904. 
