SO STDDIES IN TASMANIAN MAMMALS, LIVING AND EXTINCT, 



anterior tooth-line is firmly locked against lateral motion. 

 This is apparently correlated with the gripping of the 

 tusks upon the lateral incisors, as though the anterior 

 cheek teeth, tusks, and lateral incisors were closed down 

 upon some object to be tightly held ( n ). In bringing the 

 true molars into action (for cross grinding), the curve of 

 the total tooth-line is such as to free the premolars, and 

 they can cross and recross each other without actual con- 

 tact, and accordingly, the outer third does not in any 

 sense limit the rolling motion of the jaws under this lat- 

 ter operation. The curve of the tooth-line is aided in 

 this matter by the fact that the mandibular premolars are 

 set lower than the molars. The two factors combined pro- 

 duce the result named. 



Here then is the answer to the seeming anomaly of 

 an elongated and narrow lower premolar, being mutual- 

 ly associated with an upper, oval, tuberculated one (one- 

 third greater in width), and which, in occlusion, fits 

 tightly, and duly locks lateral motion when so required. 



In the Leptocerathine group, the animals all unduly 

 wear the anterior tooth-line, and the premolars, after a 

 time, cut their crowns under the normal action of focd 

 grinding ; the result is, such premolars are always de- 

 nuded of their cusping. The cusps in the lower premolars 

 are steeply bevelled, and, therefore, the outlines of exces- 

 sively worn teeth always appear larger than those with 

 unworn crowns. This also clears up a point ! 



As the condyle of the Nototherian jaw is exactly simi- 

 lar to that of the Wombat, the amount of cross grinding 

 action is also similar, but, as just shown, a champing and 

 gripping action is also provided for, it being only neces- 

 sary to move the contracting pressure of the jaws either 

 forward or backward, to call either into play. 



This association of such dissimilar teeth in a single 

 animal possibly throws a. sidelight on the old Protemnodon 

 and ProcojJtodou puzzle, but we have no specimens to refer 

 to 



(11) As well as serving for fighting purposes the arrangement, of the incisors 

 would he of service to the animal when gathering brandies, etc., for its food, 

 the vegetable matter being treated much as a modern wombat does with the 

 longer grasses, etc. We have observed wombats feeding amid such herbage, and 

 their sharp incisors are first brought into play in order to sever the .stem from 

 its base, after which the stem is drawn into the mouth for treatment by the 

 rnolais. Certain of the present day rhinoceroses feed on branches, etc., and 

 most probably such formed a large percentage of the food of the Nototlteria. 

 The incisive tusks and the general arrangement of the teeth would admirably 

 serve the double purpose of securing food and of being a fighting weapon of no 

 mean order. 



It might also be mentioned here that the teeth of certain species 

 of rhinoceroses of the present day serve as an indication of species. 

 In the black rhinoceros, which feeds upon branches, roots, etc., the 

 teeth are worn into alternate ridges and hollows. In the so-called 

 'white" rhinoceros, which feeds by grazing, the teeth are worn into 

 a flat plane. 



