624 



PROCEEDINGS OP THE NATIONAL MUSEUM. 



VOL. XXXVI. 



Fig. 7. — Right lowek jaw 

 OF Tkichosurus vulpe- 

 cMiL.\ Kerk. Cat. No. 

 85430. TI. S. N. M. In- 



NEU VIEW. 1 NAT. SIZE. 



has found rather wide acceptance. In his classification of the Meso- 

 zoic Mammals " Osborn stated his own views as follows : 



While the Multitiiberculata are widely separated from the mammals of the 

 second group [including the Trituberculate forms] they are so closely related 

 to each other by the unique structural and functional adaptations of the denti- 

 tion, that the discovery in one genus of a single taxonomic character, which is 

 distinctive, will probably determine their position either with the INIonotremata 

 or Marsui)ialia or in an independent order ; * * * 



The se])aration of these genera from the Diprotodonts justifies the prediction, 

 as a result of future discovery, that the Multituberculata will prove to be the 

 last representative of a very ancienf phylum which 

 reached too great a degree of specialization and den- 

 ial reduction at the close of the Cretaceous to survive 

 or leave descendents in the recent period. Whether 

 they are to be considered as a branch of the mono- 

 treme or of the marsupial stock is an unsettled 

 question. 



In his latest classification of the IMani- 

 nialia/' Osborn lists the Allotheria under the 

 subclass Protheria as a doubtful order of 

 uncertain systematic j^osition. 



Falconer and Owen referred Plaghiula.v to the Diprotodontia, but 

 ditl'ered in their opinions regarding its probable habits and taxonomic 

 relations. Falconer compared Plagiaulax with Ilypsiprymnus 

 {Poforoii.s) and sought to prove that the former was a salatory 

 herbivorous marsupial, allied to the Ivat-Kangaroos, Owen '^ just as 

 strongly contended that it was carnivorous in habits, and more prob- 

 al)ly related to the extinct carnivorous Thy- 

 lucoleo. 



Owen's conclusions regarding the. carniv- 

 orous habits of PlagktuJax lose much of their 

 force since it is now apparent, through a study 

 of the present specimen of Ptilodtis., that his 

 principal arguments were based on an error in 

 the interpretation of a most important factor, 

 namely, the normal position of the jaw. Viewing the lower jaw of 

 l*tilodv><, i)roperly articulated with the upper (see ligs. 7 and S). it is 

 observed that passing forward it pitches doAvnward at a considerable 

 angle, bringing the plane of the tooth-row below the condyle, 

 and the incisors into a semiprocumbant position as in the Diproto- 

 donts. It will be noted also that the greater j^art of the thin cutting 

 blade of p^ does not come in contact with the upper teeth, but stands 

 free in the mouth. If the lower jaw of Plagiaulax is thus placed 



a Journ. Acad. Nat. Sci. Phila. (2), IX, 1S8S, p. 254. 



6 Evolution of the Mannnalian Molar Teeth, 1907, p. 11. 



" Fossil Mammalia of the Mesozoic Formations, 1S71. 



Fig. 8. — Right lower .taw 

 OF Ptilodus gracilis. 

 Type. Inner view. 3 



NAT. SIZE. 



