THE HORSE AND THE RHINOCEROS. 67 



have a closer analogy with those of the rhinoceros* 

 than miglit at first be supposed. The anterior cres- 

 centic enamel represents the termination of the prin- 

 cipal or oblique valley, which is cut off by a bridge of 

 dentine analogous to that in the leptorhine rhinoceros. 

 The posterior crescentic island is a further develop- 

 ment of the folds in the rhinoceros' molar, but is much 

 earlier insulated in the horse. 



''•In the lower jaw the same analogies maybe traced. 

 The teeth, on the outer side, are divided into two 

 convex lobes by a median longitudinal fissure; on the 

 inner side they present three principal unequal convex 

 ridges, and an anterior and. posterior narrower ridge. 

 The crown of the grinder is penetrated from the inner 

 side by deeper and more complex folds than in the 

 anoplothere, and still more so than in the rhinoceros 



even genus, to which it belonged. The time of Cnvier marks 

 the opening of a new epoch in comparative anatomy. He ap- 

 plied this science to natural history, physiology, and to the study 

 of fossils The first edition of "Lecons d'Anatomie Comparee" 

 appeared about the beginning of the present century, and the 

 second was the last work upon which Cuvier labored. For 

 more than thirty years he had collected an immense amount of 

 facts and materials, which are partly embodied in this book. It 

 is a monument of patient industry, a model in arrangement, and ^ 

 a mine of knowledge, of whicii all observers since have availed 

 themselves. " — American Cyclopedia. 



* " The essential characteristics of the dentition of the genus 

 rhinoceros are to be found in the form and structure of the 

 molar teeth. They differ essentially from those of the horse by 

 being implanted by distinct roots. The normal dental formula 

 of the molar series is: P. M., 4-4, 4-4; M., 3-3, 3-3=28. 

 There are no canines. As to the incisors, the species vary, not 

 only in regard to their form and proportions, but also their ex- 

 istence." — Owen. 



