lOlO.] The Marsupialia. 197 



CHAPTER IV. GENETIC RELATIONS OF THE MARSUPIALIA. 



Analysis. 



Page 



I. Outline taxonomic history of the Marsupiaha 197 



II. The Polyprotodontia 200 



The Theories of DoUo and Bensley 200 



Adaptive Radiation of the Polyprotodontia 201 



Fossil Polyprotodontia 205 



Mynnecobius, the Peramelidte and Notorjictcs 208 



III. The Ca^nolestoids, or Paucituberculata 209 



The so-called " Multituberculata " of Patagonia. Are they not 



highly modified Cjenolestoids? 211 



Wyni/ardia bassiana Spencer 214 



IV. The Australian Diprotodonts 215 



Adaptive Radiation 215 



V. Summary of the arguments in favor of retaining the divisions "Poly- 

 protodontia" and "Diprotodontia" rather than "Diadactyla" 



and"Syndactyla" 217 



VI. Primitive Mammalian Characters of the Marsupial Skull 217 



Comparison of the skulls of 3/«7VHosa and i)u/eZpMs 217 



Primitive characters of the Marsupial chondrocranium .... 221 



The arrangement of the cranial foramina in Marsupials .... 222 

 VII. Taxonomic history of the divisions Prototheria, Metatheria and Eu- 



theria 225 



VIII. Summary of the Genetic Relations of the Marsupialia 225 



IX. Known Geological succession of the Marsupials and Placentals . . . 228 



X. Hypothetical succession of the Marsupials and Placentals 229 



XI. Revised diagnoses of the divisions Prototheria, Didelphia, Monodelphia 2.30 



I. Outline Taxonomic History of the Marsupialia. 



South American and Mexican opossums were described by early Spanish 

 travelers (Seba, Hernandez and others) under a number of names recorded 

 by Gesner ("Semivulpa"), Ray (1693) and Linnteus (1758). "The 

 Possvmi," "Opasum," "Possowne" (said to be an Indian word) were names 

 used by the early Virginians. In 1640 the Dutch traveller Marggrav, as 

 quoted by Ray (1693), gave a detailed description of the "Carigueija brasil- 

 iensibus" (whence the French "Sarigue), especially dwelling upon the extra- 

 uterine mode of development in the pouch, or "marsupivmi" (Ray), which 

 was mistaken for the utervis. Later it was recognized that the opossum had 

 also a true uterus, whence Linne's name "Didelphis," or double- wombed. 



