From Eocene to Recent Time 247 



belong to the genus Leuciscus This genus was al- 

 ready widely diffused in Miocene times, and it is at present 

 to be met with in the rivers and lakes of all parts of the 

 world." 



A highly suggestive feature in some of the strata is the 

 apparently seasonal succession of the deposited material, 

 alike inorganic and organic. Thus it is said: "The insect- 

 bed consists of about 250 lamellae or layers, the formation 

 of which probably occupied a long series of years, during 

 which plants and animals were deposited at all seasons 

 of the year in this book of nature. The layers that contain 

 the flowers of the camphor trees and poplars were probably 

 produced in the spring time, those which furnish winged 

 ants and the fruits of elms, poplars, and willows in the 

 summer, and those containing the fruits of the Camphor 

 trees, the Diospyros, the Clematis, and the Synantheriae 

 in the autumn. The deposits must have been formed in 

 quiet water, and at a distance from the mouth of any river. 

 Probably poisonous gases or vapors rose from this spot 

 into the air, and killed the insects flying over the water. 

 The prodigious number of species of insects here met with 

 shows us that not only the animals of the neighboring 

 shores, but those of a large area, must in the lapse of time 

 have here found their graves." 



Of the rocks and their contents belonging to the upper 

 quarry he says: "The compact indigo-blue marl which 

 covered the bottom of the lake, is overlaid by a hard bitumi- 

 nous limestone, which has received the name of Kettlestone. 

 It is the chief source of the fossil plants of Oeningen." This 

 Kettlestone also contained land and freshwater insects and 

 crustaceans, while higher up he says it is covered by a thick 

 white bed with large pike, a gigantic frog, a tortoise, and 

 a large salamander. He considers that the ground then 

 became dry, and later was submerged, when a deposit of 

 four feet of a hard limestone ("mocken,") was formed 

 in which were tench, other fishes, and aquatic plants. Next 

 "a period of perfectly still water succeeded, in which a 

 great quantity of larvae of dragon flies swam about." From 

 the fact also "that dragon fly larvae of all ages lie inter- 

 twined in certain slabs, it would appear that these insects 



