324 A MANUAL OF DENTAL ANATOMY. 



arranged without any diastema, and the transition in form 

 from the front to the back of the mouth was exceedingly 

 gradual, so that no tooth differed much from those on either 

 side of it. Taking the pattern of its molar teeth alone into 

 account, it would have been without hesitation declared to 

 be very nearly allied to rhinoceros, on which type they 

 are formed, but the resemblance fails in the canine and 

 incisor region, and it must be considered to be one of those 

 generalised types related to rhinoceros, to Hyracodon and 

 perhaps connecting them with such aberrant forms as 

 Toxodon. 



The largest of Perissodactyles equalled the elephant in 

 size, and have been named by Prof. Marsh BrontotJieridce. 

 The dental formula was 



21 43 



1 _ o _ pm _ m _. 



The incisors were small and sometimes deciduous, and the 

 canines short and stout, the lower being the more conspicuous 

 owing to its being separated by a slight diastema from the 

 premolars, which is not the case in the upper jaw. 



The premolars in both jaws increase in size from before 

 backwards, and do not differ from the molars next them. In 

 the lower jaw the premolars and molars all consist of two 

 crescents, save the last, which have three crescentic cusps. 

 The molar teeth stand apart from those of any recent peris- 

 sodactyles in their huge size, the squarish last upper molar, 

 for example, measuring four inches antero-posteriorly and 

 more than three transversely (Prof. Marsh, American Journal 

 of Science and Arts, 1876). 



