34 TERTIARY INSECTS OF NORTH AMERICA. 



size, . . . gives to the flora a general aspect which recalls that of the 

 vegetation of uplands or valleys of mountains." Palms are almost entirely 

 absent, only a single specimen of one species of Sabal having occurred, with 

 a fruit of Palmocarpon. "The leaves of some species are extrenielv numer- 

 ous, none of them crumpled, folded, or rolled, as if driven by currents, but 

 flat, as if they had been embedded in the muddy surface of the bottom when 

 falling from the trees or shrubs along the borders of a lake." 



It is remai'kable for the almost complete absence of hard fruits, and 

 this, with the presence of flowers, of unripe carpels of elm and maple, and 

 of well-preserved branches of Taxodium, which in the living species "are 

 mostly detached and thrown upon the ground in winter time or early 

 spring," led Mr Lesquereaux to believe that the deposition of tlie vegeta- 

 ble materials took place in the spring time, and that the lake gradually 

 dried during summer. 



To this we may add that the occurrence of Acorus, of Typha, and espe- 

 cially of Potamogeton, leads to the conclusion that the water of the lake 

 was fresh, and not saline or brackish, equally proved by the fish, according 

 to Cope, and by the presence of larvae of Odonata and other insects whose 

 earlier stages are passed only in fresh water. 



Neither the groups of fishes which have been found, nor the water-plants, 

 nor the water-insects, nor the mollusks exclude Mr. Lesquereux's sugges- 

 tion of the annual drying of the body of the lake ; moreover, certain thin 

 layers are found overlying coarser deposits, which are sun-cracked through 

 and through. But, on the other hand, the thickness of the paper shales, upon 

 which most of the fossil remains are found, and which are composed of 

 uniform layers of triturated flakes of volcanic products, being necessarily 

 the result of tlie long-continued action of water, excludes this idea. The 

 structure of the rocks rather indicates a quiet deposition of the materials 

 in an unruffled lake tlirough long periods, inteiTupted at intervals by the 

 influx of new lava-flows or the burying of the bottom sediments beneath 

 heavy showers of volcanic ashes. 



The testimony of the few fishes to the climate of the time is not unlike 

 that of the plants, suggesting a climate. Prof E. D. Cope informs me, like that 

 at present found in latitude 3b° in the United States; while the insects, from 

 which, when they are completely studied, we may certainly draw more 

 definite conclusions, appear from their general ensemble to prove the same 



