PAPERS ON BIOLOGY AND AGRICULTURE 



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protodonts. This reverses Dr. Osgood's conclusions, 

 based on careful and exhaustive sifting of all lines of 

 evidence save that from the nervous system. Thus 

 America is left with only extinct diprotodonts, the in- 

 ternal anatomy of whose brains we can, unfortunately, 

 never know. One might, of course, take the position that 

 the "aberrant bundle" is a character of the Australian 



T, 



13 5 



"POLYPROTODONT 



DIPROTODONT 



com d 



com v. 



COLN0LE15TLS 



Fig. 5. The aberrant bundle. Corresponding sections through the brains 



of a polyprotodont and a diprotodont (from Elliot Smith), and 



Coenolestes. 



Reference letters: cap. e., external capsule; cap. i'.. internal capsule; com. 



d., dorsal commissure ; com. v., ventral commissure ; /. ab.. aberrant 



bundle. 



diprotodonts alone, developed after the diprotodont stem 

 split in two, an Australian and an American. Dr. Os- 

 good in the final paragraph of his monograph says that 

 the classification of Coenolestes with the diprotodonts 

 "does not emphasize its supposed phylogenetic relation- 

 ship to the [polyprotodont] peramelids, but recognizes 



