314 THE GEOLOGICAL RECORD [CH. 



The Tertiary Record. 



This, as might be expected, is fairly extensive. Fossil 

 Dragonflies are known from the following beds : 



In the Eocene, the Monte Bolca beds of Italy, and the Green 

 River beds of Wyoming, U.S.A. In the Oligocene, the beds of 

 Roan Mountain, Colorado, U.S.A. (where the first fossil Corduline, 

 Stenogomphus carletoni Scudder, was found), from Sieblos in 

 Bavaria, Schlossnitz in Schleswig, Covent and Aix in France, 

 and in Baltic amber. In the Miocene, the Radoboj beds, the 

 beds of Gurnet Bay, Isle of Wight, of Falkenau in Bavaria, of 

 Florissant in Colorado, and of Oeningen in Switzerland. It is in 

 the two latter beds only that Odonata occur at all abundantly. 

 Hence we may profitably confine our attention to them alone, 

 in this chapter. 



A. The Florissant Beds. 



The chief importance of Florissant lies in the interesting 

 evidence which it affords us of the true descent of the Agrionidae. 

 The deposit is only a small one, of Miocene Age and lacustrine 

 origin. It is situated a few miles west of Pike's Peak, in Central 

 Colorado. Its present altitude is about 8000 feet. The lake 

 was about fourteen miles long, but narrow. Numerous volcanoes 

 existed in the neighbourhood. The deposit was formed of fine 

 volcanic dust, which was either washed down or fell into the 

 lake, until it was finally silted up. Insect remains are numerous, 

 in conjunction with the leaves of many interesting plants, and the 

 skeletons of fresh- water fishes. Probably most of the insects were 

 killed during eruptions, and were then washed down into the lake 

 by storms and floods. Thus they became buried in the silt, which 

 has now become a fine-grained soft shale of a greyish or buff colour. 



The flora of Florissant was of a warm temperate type. Palmetta 

 and Sequoia grew side by side with poplars and pines, while many 

 well-known Nearctic shrubs and plants seem to have been common. 

 Cockerell [45] claims that the Proteaceae were represented there. 

 But his figures of Lomatia leaves are quite unconvincing to anyone 

 who knows the Australian flora. As regards the Insecta, the most 

 abundant Order was the Hymenoptera, particularly bees and ants. 



