66 THE PERMAK^ENT DENTITIOJSr. 



"The upper grinder teeth present a modification of 

 the complex structure intermediate between the ano- 

 plotherian and ruminant patterns. The crown is 

 cubical, but is impressed on the outer surface by two 

 wide and deep longitudinal channels. It is penetrated 

 from within by a valley, which enters obliquely from 

 behind forward. This is crossed by two crescentic 

 valleys, which soon become insulated, as in the camel;* 

 but a large internal lobe, at the end of the oblique val- 

 ley, presents more of the anoplotherian proportions 

 than is shown by any ruminant. It is at first distinct ; 

 but although it soon becomes confluent with the ante- 

 rior lobe in the existing species of the horse, it con- 

 tinued distinct much longer, and with more of the con- 

 ical or columnar form, in the primigefiial horse of the 

 miocene tertiary period. 



"The grinder teeth of the horse, Cuvierf remarks, 



Remnant teeth are counted ; and, besides, the odd teeth in "both 

 animals appear in the upper jaw. Prof. T. H. Huxley says : 

 " Deei>en the valley, increase the curv^ature of the (outer) wall 

 and lam'inse (transverse ridges); give the latter a more directly 

 backward slope; cause them to develop accessory ridges and 

 pillars, and the upper molars of the tajnr will pass through the 

 structure of that of the rhinoceros to that of the horse." 



*"The dental formula of the camel is: I., 1-3,1—3; M., 

 6—0, 6—6=32. The anterior molars are conical: They are 

 separated from the posterior molars, and are sometimes regarded 

 as canines. The up.per incisors are also conical, compressed, 

 somewhat curved, resembling canines, and are used for tearing 

 up the hard and strong plants of the desert, on which the ani- 

 mal usually feeds." — American Cyclopedia. . 



f A French naturalist. Died May 13, 1832. " He is regarded 

 as the founder of the science of comparative anatomy, and his 

 knowledge of the science was such that a bone or a small frag- 

 ment of a fossil animal enabled him to determine the order, and 



