THE CHIEF COLEOPTEROUS FAUN^. 35 



opposite to each genus the diiferent countries in which they 

 are now found ; and the result shows, first, that all these Mio- 

 cene genera, excepting such as are universally distributed, are 

 now confined to my microtypal regions ; and, secondly, as re- 

 gards Europe and America, that among them are plenty of 

 genera which now inhabit both Europe and America, but not 

 one that now inhabits America and does not inhabit Europe, 

 while there are a few well marked and characterized forms, as, 

 for example, Poelohius, Oapnodis, Microzoum, and some others of 

 less marked distinction, as Perotis and Eurythyrea, which now 

 inhabit Europe and do not inhabit America. This is as strong 

 evidence in kind (I do not dispute that it might be stronger in 

 quantity, that is in number of forms), but it is as strong in 

 kind as a fossil collection from one country alone could give, that 

 the same distribution which prevails in these two continents at 

 the present time, prevailed already in the Miocene epoch. The 

 genera whicli are now peculiar to Europe were then peculiar to 

 it, and, consequently, the inference is strong that no communi- 

 cation between the two countries has ever existed since the days 

 when these fossil insects were in life. If we had an xlmerican 

 collection of the same age in which types now peculiar to 

 America were found, the evidence would of course be still 

 stronger, but it would be repetition of what we have already 

 observed in Europe. The same relations between the Ameri- 

 can and European Miocene species are to be found in other 

 classes. I give a somewhat less elaborate (as regards num- 

 ber of regions) list of the distribution of all the other existing 

 genera of insects recorded by Heer and Krantz, not only for its 

 bearing on this inquiry, but in the expectation that it may be 

 convenient and useful to other students of geographical distribu- 

 tion to have such a list at hand. The Hemiptera have been gone 

 over for me by Mr. Dallas, our first authority on that branch, and 

 the table and notes embrace the information derived from him, 

 although he is not responsible for it all, his attention having been 

 only specially requested to Europe and America. In that table 

 it will be seen that the Miocene genera Prostemma, Nepa, and 

 Diplonychus, and in the Homoptera the genus Tettigometra, are 

 now found in Europe and not in America, and that one or two 

 instances where the reverse seems to be the case are due to 

 modern alterations on the genera used by Heer. In the Diptera it 

 will be seen that all the genera are both American and European. 



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