GENERAL CHARACTERISTICS. 



iS: 



have its cusps of a sharp-pointed conical a manner as to assume exactly the charac- 

 form, but in many cases it scarcely tlifters teristic form of the teeth of the Insectivora, 

 in form from the true molars which come so that one could not tell their orioin if thev 



after it. The latter usually have sharp- 

 pointed cusps on the outer edge, and are 

 prolonged into a narrow internal heel in such 



were found singly. On the other hand, we 

 observe in some genera a well-marked 

 tendency in the dentition to become adapted 



Fig. 89. — The Common uenet [iicrwrta z'laoarn). page i5t). 



to a mixed diet. The crowns then become 

 broad, almost quadrangular, the tubercles 

 become blunt and o-et so worn away that 

 in the latter years ot the animal's life they 

 present to view almost e\'en surfaces. 



The tendency to a progressive specializa- 

 tion of the teeth is strikino-ly shown on a 

 comparison of the milk with the permanent 

 dentition of these animals. The premolars 

 of the milk dentition are manifestly in- 

 sectivore teeth, with sharp points which tit 

 into those of the opposite jaw. I reckon 

 with Owen three premolars above and below 

 in the milk dentition of the suricate. The 

 second deciduous premolar of the upper jaw 

 has five sharp points, and by its form and 

 size plays the part of a carnassial ; the third 

 has only three points, and resembles a 

 permanent molar. Now in the permanent 



dentition the large five-pointed tooth is 

 replaced by a conical tooth, and it is the last 

 of the second set ot teeth which becomes 

 the permanent carnassial. The same thing 

 happens in the lower jaw. The last pre- 

 molar is, in the milk dentition, a carnassial 

 with points : but in the permanent dentition 

 it is replaced by a simple conical tooth, and 

 the first permanent molar becomes the 

 carnassial. 



The total number of the teeth in the 

 permanent dentition varies according to the 

 development of the premolars. There are 

 always two true molars in each half of the 

 jaw, but there may be three or four premolars. 

 The formulas of the permanent dentition are 

 I • — 2 , ;, ■ I • 4 • 2 



thus: " 



36, or 



40. 



I • 4 ■ 2 

 The species which have been examined with 



