70 BRITISH ORTHOPTER.A. 



several examples of the Blattodea ; but apparently 

 none have come to Ii2rht in this country. 



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Passing to Mesozoic times the Triassic rocks of 

 America have produced a number of specimens of the 

 Blattodea, but tins is not the case in Europe. In the 

 Lias fossil insects are numerous, and examples of 

 those we are considering are represented both in 

 Britain and on the Continent. The Purbeck beds of 

 the Upper Oolite have preserved several species, but 

 they appear to be absent from the Cretaceous forma- 

 tions, as we should expect, seeing that a large pro- 

 portion of these rocks are of marine origin and were 

 deposited in deep water. 



In Cainozoic times the Eocene period does not seem 

 to have produced fossil cockroaches in Britain, but 

 perhaps the conditions, under which the formations 

 during the period were deposited, were not favourable 

 to their preservation. The rest of the Tertiary forma- 

 tions are absent , from, or not well represented in 

 Britain ; but the Blattodea have left some remains in 

 Miocene strata on the Continent, and a few have been 

 preserved in amber. In the Post-tertiary period 

 fossil insects are rare, except Coleoptera, to which 

 Order all must perhaps be referred. 



Judging by the wings, from which almost entirely 

 our knowledge of fossil cockroaches is derived, these 

 insects are found to bear a close general resemblance 

 to recent forms. They, however, present three impor- 

 tant differences. First, the elytra and wings were 

 similar in appearance and transparent; second, the 

 same number of nervures was developed in both, 

 whereas in recent forms they are reduced in number 

 in the elytra ; third, the arrangement of the nervures 

 in the anal area was different. In fact the wino\s, 



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rather than the elytra, of recent cockroaches preserve 

 more closely the appearance of both wings and elytra 

 of fossil forms. Since Palaeozoic times cockroaches 

 appear to have decreased in numbers greatly, if not so 

 much in sL?e, and they must now be looked upon as 



