ORDINAL TYPES OF MOLARS: MARSUPIALIA 



111 



Pa' 



\ 



V<| 



\ -fc^*s 



^m-^ 



En d - 



Lower Molars of the Left Side. 



Flu. os, Xo. '2. Adaptive Radiation of the Tritubeivular Molar Type in the Marsupialia 

 (continued). From Bensley. (Cf. Fig. 58, X. 1.) 



o, b, c, Insectivorous type. , Oligocene Opossum (Peral/ni-inin .""""'); !l , Recent Opossum 

 (Diilelphii.i a :i.i i-ii 1 ); c, DiiU-l/ilii/x cu-'juiinnu . n , t1, ;/, Progressive carnivorous specialization. 

 (', Daxyui-ux viverrinus \ <i, Thtilnri/,t,'.-: ,-n,tm; jilmlun. c, Progressive insectivorous-omnivorous 

 type (Pi rameles nasntn); f, Omnivorous to herbivorous type (I'ltmii-niiiix i-i>/n,ix). It, Incipient 

 lophodont, herbivorous type (Trichosurv.x I'ul/n'i'ulu). i, Perfected lophodout, herbivorous type 

 (Macropits sp.). j, Selenodont herbivorous tj - pe (P/iascolarctos cinert i> .-). 



nasi it a (Fig. 58, No. 2, c} persistently resemble still more closely those 

 of Das//t>i"vv, the omnivorous modification being only developed in the 

 posterior heel where the hypoconulid is reduced. 



Perfected Omnivorous Marsupials. 



The perfected omnivorous modification among Marsupials is met 

 with in the Phalangeridse. The two examples of the Phalangers 

 examined by Bensley were Tricliosurus rnlpecida, in which the molars 

 are highly specialized, and Petanroides volans, the teeth of the latter 

 being represented in Fig. 58, /. Although these teeth illustrate the 

 completed quadritubercular condition, they are only approximately transi- 

 tional ; as among the Placentals, the hypocone is completely formed 

 in the upper molars and the paraconid is correspondingly reduced 



