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Icon, of which there are three known species — one from 

 the Upper Trias of Queensland, one from the Lower Lias 

 of Western England, and one from the Upper Lias of 

 Northern Germany (see Tillyard, 1925). Most of the 

 Liassic dragon-flies belong to an order Anisozygoptera of 

 which the wing- form recalls that of the recent Anisoptera, 

 but the neuration is less specialised. Several distinct 

 families of Anisozygoptera are known from the Lias and a 

 single genus (Epiophlebia) survives to-day in Japan and 

 Northern India. In Jurassic rocks of later age than the 

 Lias are preserved remains of dragon-flies approximating 

 closely to the existing families which have come down from 

 the late Secondary and early Tertiary times to the present 

 day with little change in form and life-history. 



The Plecoptera (Stoneflies) also had their precursors 

 in the Palaeozoic era. Tillyard (1926) describes the members 

 of an extinct order, Protoperlaria, as a '' dominant type of 

 insect " among the series of fossils lately discovered in the 

 Lower Permian beds of Kansas in North America. *' Some 

 of these are preserved perfectly in every detail and show a 

 very unexpected character in the presence of well-formed 

 wing-flaps with extensive venation on the sides of the pro- 

 thorax." Such abortive winglets recall the similar structures 

 noticed already in certain Carboniferous Palaeodictyoptera 

 to which the ancestral stoneflies were in all probability 

 closely related. From the Kansas Permian beds have been 

 disinterred also remains of early members of other allied 

 groups such as Embiidae and Psocids. 



Among the Exopterygota the Hemiptera, with their 

 jaws specialised for sucking and piercing, form a large and 

 very distinct order. The well-known fossil insect Eugereon, 

 from rocks of Permian age in Germany (Oldenburg) shows 

 a head with apparently typical bug- like beak and piercers, 

 while the thorax bears palaeodictyopteroid wings. It seems 

 evident, therefore, that the precursors of the Hemiptera had 

 undergone radical change in the structure and function of 

 their jaws while their wings still retained primitive form and 

 neuration. Tillyard has, however, demonstrated (1926) 



