1883.] NATURAL SCIENCES OF PHILADELPHIA. 269 



Dipus and Hystrix,^ be sufficient, as far as the mammalian fauna 

 is concerned, to separate tliat region from the Palaearctic, could 

 not on nearly equally strong grounds a separation be effected in 

 the Paltearctic region itself? Thus, if we were to consider the 

 western division of the Palaearctic region, or what corresponds 

 to the continent of Europe of geographers, as constituting an 

 independent region of its own, it would be distinguished from 

 the remainder of what now belongs to the Palaearctic region by 

 negative characters probably fully as important as those indicated 

 by Mr. Wallace as separating the Nearctic from the Palaearctic 

 region. The European mammalian fauna would be wholly 

 deficient, or nearly so, in the genera Equus, Moschiis, Camelus, 

 Poephagus, Gazella, Oryx, Addox, Saiga, Ovis^ Lagomys, Tamias, 

 in several of the larger Felidse, as the tiger and leopard, and in 

 a host of other forms. A similar selection coiild be made from 

 the class of birds (among the most striking of these the Phasi- 

 anidse and Strutliionidae) , but it is scarcely necessary in this place 

 to enter upon an enumeration of characteristic forms. Divisions 

 of this kind, to be characterized principally or largely by nega- 

 tive faunal features, could be effected in all the regions, and in 

 some instances with probabl}'^ more reason than in the case under 

 discussion. 



" But the question suggests itself, what amount of characters, 

 whether positive or negative, or both, is sufficient to distinguish 

 one regional fauna from another ? Mr. Wallace states : ' There 

 runs thi'ough Prof. Ileilprin's paper a tacit assumption that there 

 should be an equivalence, if not an absolute equality, in the 

 zoological characteristics and peculiarities of all the regions.' 

 Is it to be inferred from this quotation that Mr. Wallace recog- 

 nizes -no such general equivalence? Is a region holding in its 

 fauna, say from 15 to 20 per cent, of peculiar or highly charac- 

 teristic forms, to be considered equivalent in value to one where 

 the faunal peculiarity amounts to 60 to 80 per cent. ? If there 

 be no equivalence of any kind required, why not give to manj'^ of 

 the subregions, as now recognized, the full value of region ? 



" Surely, on this method of looking at the question, a province 

 could readily be raised to the rank of a full region. In the 

 matter of geographical individuality little need be said, as the 

 circumstance, whether it be or be not so, that the 'temperate 

 and cold parts of the globe are necessarily less marked by highly 



