1GG DISTRIBUTION OF EXTINCT ANIMALS. [part ii. 



is allied to the Menopoma living in North America. Species 

 of frog (Bana), and Palceophryus an extinct genus of toads, 

 have been found in the Miocene deposits of Germany and 

 Switzerland. 



Fresh water fish are almost unknown in the Tertiary 

 deposits of Europe, although most of the families and some 

 genera of living marine fish are represented from the Eocene 

 downwards. 



Antiquity of the Geneka of Insects. 



Fossil insects are far too rarely found, to aid us in our determi- 

 nation of difficult questions of geographical distribution ; but in 

 discussing these questions it will be important to know, whether 

 we are to look upon the existing generic forms of insects as of 

 gieat or small antiquity, compared with the higher vertebrates ; 

 and to decide this question the materials at our command are 

 ample. 



The conditions requisite for the preservation of insects in a 

 fossil state are no doubt very local and peculiar ; the result being, 

 that it is only at long intervals in the geological record that we 

 meet with remains of insects in a recognisable condition. None 

 appear to have been found in the Pliocene formation ; but in the 

 Upper Miocene of (Eninghen in Switzerland, associated with the 

 wonderfully rich fossil flora, are found immense quantities of 

 insects. Prof. Heer examined more than 5,000 specimens be- 

 longing to over 800 species, and many have been found in other 

 localities in Switzerland ; so that more than 1,300 species of 

 Miocene insects have now been determined. Most of the orders 

 are represented, but the beetles (Coleoptera) are far the most 

 abundant. Almost all belong to existing genera, and the majority 

 of these genera now inhabit Europe, only three or four being 

 exclusively Indian, African, or American. 



In the Lower Miocene of Croatia there is another rich de- 

 posit of insects, somewhat more tropical in character, comprising 

 large white-ants and dragon-flies differently marked from any 



