316 THE GEOLOGICAL RECORD [CH . 



from the wing-base. The Neotropical genus Thaumatoneura is 

 another Megapodagrionine remnant which has stopped at about 

 the stage exhibited by Phenacolestes in the Miocene; but it is 

 not so closely related to the latter as are some existing genera 

 with only two antenodals. Calvert[33] has recently discussed 

 Phenacolestes very fully in an excellent paper, to which the reader 

 is referred for further information. 



Cockerel! [44] placed Dysagrion, from the Oligocene of the Green 

 River beds, together with Phenacolestes, in a new subfamily 

 Dysagrioninae. It is clear that this subfamily cannot stand, but 

 must be merged in the Megapodagrioninae. The restored wing 

 of Phenacolestes makes this quite evident. 



Another interesting Agrionid, with two antenodals, and a 

 general close resemblance to Argia, was described by Scudder 

 as Trichocnemis aliena. The generic placing is here evidently 

 wrong. An Agrionid larva with caudal gills complete has also 

 been found. Scudder described it as Agrion telluris. But the 

 remarkable banded pattern of the legs is very marked in the 

 Megapodagrioninae, to which subfamily this larva probably 

 belonged. 



B. The Oeningen Beds. 



The Oeningen beds are situated in the Rhine Valley, between 

 the towns of Constance and Schaffhausen in Switzerland. They 

 consist of a series of marls, sandstones and limestones, some being 

 marine and some fresh-water. Beds of brown coal are interpolated 

 here and there. It is the uppermost strata which contain the 

 insects, in company with the remains of fresh-water fishes, a few 

 Crustacea, reptiles, birds and mammals, a number of Arachnida, 

 the very common bivalve Anodonta, and an abundant flora 

 shewing distinct Nearctic affinities. The complete formation 

 covers the whole of the flat lands of Switzerland, some 150 square 

 miles, and is of considerable thickness. The uppermost strata 

 are known as the Upper Fresh-water Molasse, and are of late or 

 Upper Miocene age. 



More than three hundred species of insects are known from 

 these beds, which have evidently been formed by slow accumulation 

 of sediments in a lake fed by springs of water strongly impregnated 



