XVI] THE GEOLOGICAL RECORD 313 



that these beds are in reality exceedingly poor in specimens. 

 It would be impossible for anyone, visiting the quarries, to pick 

 up more than one or two fossils, even though he searched assiduously 

 for days. It is only because of the commercial value of the slate, 

 which is in great demand by lithographers } and the consequent 

 opening up of immense quarries extending for many miles, from 

 which millions of tons of stone have been stripped, that we can 

 reckon the total of Solenhofen fossils as a great one, and, in the 

 case of the Odonata, exceeding in number and variety the total 

 from any other beds known to us. Every fossil has been carefully 

 preserved by the workmen, who obtain high prices for them, 

 chiefly because of the exquisite outline of the impressions in the 

 fine-grained slate. 



The colour of the stone is for the most part pale ochreous, 

 and so finely grained as to appear artificially smoothed. At first 

 sight, one of the Solenhofen Dragonflies might well be taken for 

 a "fake," so exquisitely is the outline of body and wing preserved. 

 It is only when one comes to study the details of venation that 

 the disadvantages of this fine grain become obvious, many of the 

 finer cross-veins being found to be almost or quite obliterated. 

 This detracts much from the value of the fossils for detailed 

 study. Their charm lies chiefly in the perfection of outline and 

 of the main venational plan. 



In concluding this account of Solenhofen, it may be remarked 

 that we cannot expect these beds to yield much further information 

 in the future. They have been very extensively worked, and 

 it seems most unlikely that any more new forms will be found. 

 We may, however, still hope for the discovery of better preserved 

 specimens of some of the more interesting genera, from which 

 to gain further information of their finer venational characters. 



C. The Cretaceous Dragonflies. 



The only Cretaceous fossil Dragonfly known is Aeschnidium 

 flindersiense Woodward. It was found, in company with the 

 fresh-water bivalve Aucella, in the chocolate-coloured limestone 

 of the Flinders River beds in Queensland. It shews us that the 

 Aeschnidiinae were once widely spread, and perhaps lingered on in 

 Australia after their extinction elsewhere. 



