1883.] NATURAL SCIENCES OF PHILADELPHIA. 271 



lates. Prof. Heilpriii being a skilful dialectician and well 

 informed, has submitted a prett}^ argument in favor of the union 

 of the North American or ' Xearetic ' and Eurasiatic or ' Palae- 

 arctic' regions (Proc. Acad. Nat. Sci. Phil., 1882, pp. 316-334, 

 and Nature, vol. xxvii, p. 606), but Mr. Wallace has, with perfect 

 justness it seems to me, objected to his proposition (Natu7'e, vol. 

 xxvii, pp. 482. 483). As Prof. Heilprin's arguments have not 

 been entirelj^ met, however, permit me to submit some further 

 objections to his views. 



" Prof. Heilprin has contended ' (1) that by famil}-, generic, 

 and specific characters, as far as the mammalia are concerned, 

 the Nearctic and Palsearctic faunas taken collectively are more 

 clearly defined from any or all of the other regions than either 

 the Nearctic or Pala?arctic taken individually; and (2) that by 

 the community- of family, generic and specific characters the 

 Nearctic region is indisputabl3' united to the Palasarctic, of which 

 it forms a lateral extension.' 



" Prof. Heilprin has formulated these conclusions after a sum- 

 maiy of the families and genera common and peculiar to the 

 regions in question. 



"As to families Prof. Heilprin has pi'esented the following 

 figures : — 



Nearctic, 



Paljiearctic, ..... 

 Oriental, ..... 

 Australian, ..... 

 Ethiopian, ..... 

 Neotropical, .... 



" The proportions of peculiar genera to the entire mammalian 

 faunas of the several regions are stated to be as follows : — 



All. Peculiar. Percentage. 



Nearctic, .... 14 26 35 



Palaearctic, . 



Oriental, 



Australian, . 

 Ethiopian, . 

 Neotropical, 



100 35 35 



118 54 46 



70 45 64 



142 90 63 



131 103 78 



The question may naturally recur, why the line which sep- 



