250 



rsrcnE. 



[J;niu;iry — Murch 1SS5. 



sixty-six troin Europe and thirteen from 

 America, eigiit being common to both. 

 Of tiiese 37 are accounted extinct, 35 

 from Europe and 2 from America, and 

 none of these have been found on both 

 continents. 



In the stratified tertiary deposits the 

 same families of araneae are in e\ery 

 instance found in Europe and America, 

 excepting the dysderides. which family 

 has a single representative in America 

 and none in Europe. It also appears 

 that just those families which are repre- 

 sented abundantly in amber are also 

 found to some extent in the American 

 tertiary fauna, and (excepting, as be- 

 fore, the dysderides) in the European 

 rocks. 



It is onl}' in the rocks of the temper- 



ate regions of Europe and Nortli Amer- 

 ica that any arachnida liave been found 

 in a fossil state, and these, so far as the 

 indications have any meaning, invari- 

 ably point, whether in carboniferous or 

 tertiarx deposits, to a warmer climate 

 than now obtains in the localities where 

 thev occur. This becomes more marked 

 when we reach the tertiary rocks and 

 can compare the t\pes more closely 

 with existing forms, a number of the 

 genera, to which, for instance, the amber 

 spiders belong, being now exclusively 

 tropical. 



The following table gives a general 

 systematic view of the distribution of 

 arachnida in the diflerent geological 

 formations since their first appearance 

 in the upper silurian. 



Geological distribution of arachnida. 



