MAY, 1921. AMERICAN MARSUPIAL, C^NOLESTES OSGOOD. 69 



a single vagina, but is regarded as a special development not necessarily 

 leading to nor derived directly from the single eutherian vagina. That 

 it should have been independently developed in different phyla seems 

 highly improbable. Hill's statement (p. 74) in regard to this is as fol- 

 lows: "That this median passage has not been twice independently 

 acquired within the Marsupial Class I am convinced, and its existence 

 in Perameles in a condition so obviously unspecialized and in association 

 with such a persistently embryonic condition of the genital organs, 

 tends to suggest that its acquisition is of ancient date." Elsewhere he 

 says: "Finally, as regards parturition, it seems to me that the foregoing 

 discussion sufficiently upholds the conclusion that Perameles, in respect 

 to the phenomena connected with that process, in no way stands alone 

 amongst Marsupials as an aberrant and specialized type, but quite on 

 the contrary, exhibits more primitive features in the mode of birth of 

 the young than are shown by any other Marsupial hitherto described 

 as possessing a direct median passage. That the direct passage in 

 Perameles is in a much more primitive condition than that of Macropods, 

 will, I think, be admitted without question. Indeed, the condition of 

 the passage in Perameles can only, in my opinion, be regarded as the 

 precursor of the Macropine one and as showing us in use today the 

 earliest stage in the evolution of that direct median passage which 

 reaches its highest development in the specialized Macropodidae." 



So far as gross examination indicates, Canolestes is more advanced 

 than Perameles and, although final proof must await microscopic study 

 of serial sections, all the present evidence points to the conclusion that 

 the direct median passage is nearly or quite as well-developed in Coeno- 

 lestes as it is in various Australian diprotodonts. In a virgin female, the 

 median cul de sac extends almost to contact with the urogenital sinus 

 and in an old female, openings were found in the vaginae and the adjacent 

 surface of the sinus, but the connection between them was imperfect 

 and possibly due to adventitious circumstances in the history of this 

 particular specimen. 



ALIMENTARY CANAL. 



Mouth. The hard palate has numerous transverse ridges. In- 

 cluding the one at the posterior edge of the palate, there are nine of 

 these ridges that extend completely across the palate and five which do 

 not but merely reach to varying points on either side of the median line 

 (PI. XVIII, Fig. 3). The ridge between the last molars has 8 to 10 

 forwardly directed protuberances giving it a somewhat serrate appear- 

 ance. The ridge between or just behind the canines projects forward in 



