226 PAST DISTRIBUTION OF MARSUPIALS. [CH. V 



argued a sea occupying the region of the Sahara (luring 

 tertiary times are now believed to have been erroneous. 

 Zittel, says Mr Blanford, has shown that there is no reason 

 to think that any part of the Sahara has been sea since 

 the Cretaceous period. This fits in admirably with the 

 present and past distribution of the Marsupials and in quite 

 a convincing way. There is of course abundant evidence 

 that these mammals were common in Europe during the 

 mesozoic epoch, whether they originated there or not. 

 Now if there was then land connection with the African 

 continent why did they not migrate there as well as to 

 Australia and to America ? It is of course possible that 

 they did and that they have since become extinct. 

 Madagascar however has to be considered ; many writers 

 have pointed out that Madagascar appears to have 

 preserved some of the more ancient mammalian inhabi- 

 A tants of the Ethiopian continent. In any case it seems 

 .certain that many of the newer immigrants into Africa 

 never succeeded in getting as far as Madagascar. There 

 are so many analogies of a kind between Madagascar and 

 Australia that the negative fact that Marsupials do not 

 occur there gets a certain importance. If however the 

 severance between Africa and Europe was of earlier date 

 than is commonly held we have a possible explanation of 

 the entire (?) absence of Marsupials from the former 

 continent. Besides, their absence sheds perhaps an 

 oblique light upon my suggestion that the group origin- 

 ated in Australia. The numbers in Europe may have 

 been small, and there was therefore no pressure such as to 

 lead to migration. 



