310 



THE GEOLOGICAL RECORD 



[CH. 



B. The Jurassic Dragonflies. 



The record of the Upper Jurassic beds is not only very complete, 

 but is the most valuable chapter of Odonate phylogeny that has 

 yet been revealed to us. From the Dogger of Ust Balei, Siberia, 

 we have a series of records of Dragonfly larvae, the Samarnrinae. 

 These had no lateral abdominal gills, but three short oval caudal 

 gills. They may be provisionally classed as Calopterygidae. 

 In Britain, the Purbeck beds, and the Stonesfield Slates of Oxford, 

 supply a few interesting fossils. But it is to the splendid mass 

 of material derived from the lithographic slates of Solenhofen and 

 Eichstatt in Bavaria that we owe our chief knowledge of the 

 Dragonflies of this horizon [60]. 



These beds are probably best known because of the discovery 

 there of the wonderful fossil Archaeopteryx, which so beautifully 

 links the Birds with the Reptiles. Thus, as students of the 

 Odonata, we gaze for the last time upon the remnants of the former 

 giant race, the Kings of the Air, whose domain is now about to 

 be wrested from them by the Birds. From henceforth they are 

 condemned to follow the difficult path of high specialization 

 either for rapid flight or for concealment, if they are to escape 

 destruction at the hands of their more powerful enemies. 



A remnant of the Palaeozoic giants is found in the wonderful 

 subfamily Isophlebiinae, of which 

 the best known species is Isophle- 

 bia aspasia Hagen (fig. 161). This 

 beautiful insect had a slender body 

 six inches long, while the expanse 

 of its wings was about eight inches. 

 The wings were long and slender, 

 and evidently of Calopterygid de- 

 sign, except for the peculiar struc- 

 ture of the anal area, particularly 

 noticeable in the hind-wing. Cu 2 

 descends sharply from the quadri- 

 lateral, and gives off a proximal Fig 16] p or tion of bases of wings 

 branch almost meeting the strongly of Isophlebia aspasia Hagen 



... (xl), Upper Jurassic. Solen- 



curved anal vein at its ending on hofen After Hagen. 



