371 



ing countries will uftcn throw greai ligliL iipon the geolo- 

 ST, and enable us to tracé out witli tolerable ccrtaintv 

 its past liistory. A consicleration of the birds of Am 

 has led us at sorae lenglit into this subject, both on 

 account of the interest attached to it, and because we 

 are not aware of any attempt to explain in detail how the 

 existing distribution of species hasarisen, or strictl}- tocon- 

 nect it with those changes of sarface vvhich all countries 

 have undergone. The Birds and Mammalia onlj' have been 

 used for illustration , because they are much better known 

 than any other groups. The Insects , however , of which I 

 have made a very extensive coUection , fiirnish exactly 

 similar results, and were these, particularly the Cole- 

 optera, well known, they would perhaps be preferable 

 to any group for such an inquiry , from the great num- 

 ber of their genera and species, and the very limited 

 range which roany of theni attain. In imperfectly ex- 

 plored contries, however, Birds are almost always bet- 

 ter known than any other group, as a larger propor- 

 tion of the \Nhole nuuiber of species may be obtained 

 in a limited time. I think it probable that 1 have 

 coUected more than half the birds inhabiting Aru, whi- 

 le I do not iniagine I have obtained one lifth part of 

 the Insects. The following is a brief summary of my 

 coUections in this class : — 



Coleoptera 572 species. 



Lepicloptera 229 'f 



Ilymenoptera. 214 // 



Diptcra 1S5 // 



Ileuiiptera and llomoptera. . 130 // 

 Orthuplcra and Neuroptcra &. . 34 // 



Making a total of 1304 species. 



