412 



THE NATURAL HISTOET EEVIEW. 



anterior collis, D, obliquely backwards and inwards as far as the neck 

 of tbe tooth, and is continuous witb the small guard that passes trans- 

 versely from the outer to the inner side of the anterior aspect. 

 These two points diiQferentiate the megarhine from both the other 



Fig. 14 



species. The tumidity of the areas, M N, which compose the external 

 laminge, and the absence of ribs from the anterior area are also 

 salient points of difference in the lower molar series (See Pig. 15). 

 The posterior fang of M 3 is cylindrical in section and reflected, 

 which is never the case with the other teeth. The obliquity of the 

 wear of the enamel on the outer aspect, owing to a different habit of 

 mastication, as compared with its even wear in the tichorhine species, 

 is worthy of note. 



§ 5. Measurements. The measurements taken at the base of the 

 crown in inches and tenths, are uniform with those used in my 

 essay on the Dentition of the tichorhine Ehinoceros. (Nat. Hist. 

 Eev. iii. p. 525.) They are : — 



1. Antero-posterior, taken along the outside of crown. 



2. Antero-transverse, taken across the anterior lobe of the tooth. 



3. Postero-transverse, „ „ posterior „ „ 



