74 MAMMALIAN DENTITION 



are almost transverse since these teeth are no longer required 

 .as forceps but form rasps for cleaning flesh from bones. 



The canines are powerfully developed as is natural in a 

 carnivorous type. 



In the molars the development of shearing action is pro- 

 nounced and all triturating function is practically eliminated. 

 In conformity with the adaptation of the molars to a pure 

 shearing function the following modifications have occurred. 

 In the upper teeth the protocone and paracone are reduced 

 and the two anterior styles are nonexistent. On the other 

 hand the metacone and metastyle are greatly developed. With 

 the reduction of the protocone the hinder margin of the tooth 

 swings round to bring the shearing edge more in line with the 

 direction of the dental arch. This will be apparent if a 

 ruler is applied on the figure to touch the metastyle and 

 metacone of the third upper molar. The straight edge will 

 pass across the second premolar of the opposite side. If the 

 same test is applied to the third upper molar of Phascologale, 

 the straight edge will pass through the second molar of the 

 opposite side. In the lower molars the protoconid and para- 

 conid are strongly developed and together form a shearing edge. 

 The metacone is nonexistent though it is represented on the 

 last tooth by a small cingular cusp. In all the talonid is greatly 

 reduced, being represented by a small entoconid and an ob- 

 viously decadent hypoconid. The last upper molar having no 

 shearing function is very degenerate and since there is prac- 

 tically no protocone on this tooth the talonid of the last lower 

 molar is also vestigial. 



Another type of carnivorous adaptation, this time retaining 

 the long jaw, is represented by Thylacinus cynocephalus, the 

 Tasmanian Wolf (Fig. 20). The most striking feature of this 

 animal which is larger than and almost equally ferocious with 

 Sarcophilus is the fact that the jaws instead of being fore- 

 shortened are lengthened, especially in the premolar region. 

 This elongation has not interfered with the typical carniv- 

 orous arrangement of the incisors but has resulted in the re- 



