MAY, 1921. AMERICAN MARSUPIAL, C^NOLESTES OSGOOD. 147 



perhaps in Cretaceous times by means of an Antarctic land bridge. 

 Further evidence of the former existence of such a bridge is afforded by 

 plants, mollusks, crustaceans, insects, amphibians, reptiles, and other 

 forms of life of which closely allied species are now found inhabiting 

 both Australia and southern South America. Enumeration of these 

 forms has been made at great length by various authors and need not 

 be repeated. It is sufficient to admit that the evidence is very extensive 

 and if the southern continent be supposed to have been one of no great 

 permanence, but, as Hedley (1895) has indicated, may have been attenu- 

 ated, irregular and unstable at many points, belief in its existence is 

 greatly strengthened and the objections based upon geological and 

 isostatic data do not weigh so heavily against it. To cite only a few 

 of the believers in Antarctica, it may be said that among its most 

 recent adherents have been Sinclair (1906), Ortmann (1905), Scott 

 (1913), and Osborn (1910). One of its earliest and most distinguished 

 advocates was Huxley. In general it seems to have been conceded that 

 with so much and so varied evidence there could be little doubt that 

 some sort of connection must have existed. The northern origin of many 

 and very important groups, however, could scarcely be denied and the 

 general theory of mammalian dispersal was thus a bipolar theory. 

 Nevertheless the Argentine paleontologist Ameghino went so far as 

 to regard South America as the original home and center of dispersal 

 of practically all the larger groups of mammals. 



In contradistinction to these views and in reversal of his own previ- 

 ous acquiescence to belief in Antarctica, Matthew (1915) has presented 

 a powerful argument for the dispersal of mammalian life exclusively 

 from Holarctic centers. 1 His conclusions are based upon a broad and 

 comprehensive survey of geological and biological data and the similari- 

 ties between certain southern faunas are regarded as exceptions to the 

 general rule to be explained either by the imperfection of the paleonto- 

 logical record, by natural raft transportation, or by convergent evolution. 

 The case of Ceenokstes is mentioned by Matthew and treated as one of 

 convergence, the views of Broom and Dederer as to its polyprotodont 

 affinities being accepted. A similar view of Ccenolestes and its allies 

 has been taken by Gregory. The present study does not favor a great 

 degree of convergence, but it tends to substantiate the opinion that an 

 Antarctic land connection is not required to explain the presence of 

 C&nolestes in South America. 



The many resemblances which C&nolestes shows to the Australian 



north polar theory had been presented also by Haacke in 1887 and by 

 Haseman in 1912. 



