278 Review of Saporta’s Work 
evaporation and gradual drainage, the area of the lakes or a 
swamps being gradually diminished by shrinkage, the fishes 
were driven into deeper places, where finally enclosed they 
perished in masses. eir remains were later covered by 
the muddy water of the next overflow in the rainy season. In 
that immense formation of the Green River group, no trace of 
effects of voleanic agency is seen. It has been through its 
whole thickness a series of quiet, lacustrine deposits of calcare- 
ous clays, during an incalculable period of time 
River station, for example, from the bottom of the river to the 
top of the highest red buttes, about six hundred feet in thickness, 
the whole series is a succession of those laminated shales, vary- 
ing only in their constituent beds, there being white calcareous 
clay, greenish, sandy, red ferruginous clay, in an uninterrupted 
succession of thin layers. 
Considering the data furnished by the plants in reference to 
the synchronism of the Green River formation, it is only re- 
found there in connection with or upon the same specimens 
with a Pterospermites, a Hedera, and Sequoia Langsdorffi. It 1s 
ne TRE ee a ee ee 
