212 The American Naturalist 



[March, 



The similarities and contrasts between the fauna of the Bear River 

 formation and those of the other nonmarine beds of North America 

 leads to a discussion of their causes. The author suggests that certain 

 genetic lines of descent have become diverged from the main lines of 

 succession and destroyed by some of those physical changes which mark 

 successive epochs, and adds " we may reasonably assume that one of 

 those divergent lines terminated in the Bear River fauna ; that is, at 

 the close of the Bear River epoch the area which its nonmarine waters 

 had occupied having become overspread by the marine waters in which 

 the Colorado formation was deposited, it is not probable that any 

 fluvial outlet of the former nonmarine waters was perpetuated, and 

 there was, therefore, no provisional habitat in which the Bear River 

 fauna might have been preserved. It was probably in this way that 

 the distinguishing types of that fauna became extinct, together with 

 others of its members which were not so specially characteristic of it." 

 (Bull. U. S. Geol. Surv. 128, Washington, 1895.) 



On the Occurrence of Neocene Marine Diatomaceae near 

 New York.— The rocks which contain Diatomaceie (or Bacillariacese) 

 in America are clayey, that is to say they contain more or less of clay, 

 and they vary in color from a nearly white to a fawn color and to a 

 greenish, greyish-brownish or almost black. They are not older than 

 the Oligocene nor newer than the Plistocene. They can be placed in 

 the Neocene, a period that ranges from the Eocene to the Plisto- 

 cene, and not in the recent. Those I have to describe in New York 

 are not Miocene, but they belong to a place which may provisionally 

 be classed as Pliocene or Plistocene of the European geologists. 



Ever since 1843, the so-called infusorial earth has been known in 

 Virginia and was thought by Rogers the discoverer to be Miocene 

 Tertiary, he classifying it as the European rocks were. Bailey accepted 

 the classification and so did the later geologists. When fresh water 

 fossil'Diatomacese were found in Massachusetts they were thought to be 

 Miocene also without studying the rocks themselves and seeing how 

 they stood in the geological scale. When they were found in New 

 Hampshire I did not classify them nor did Hitchcock attempt to do so. 

 They were placed in the lacustrine Sedimentary and provisionally in 

 the!Recent. But now they can be seen to be older than the Recent 

 and|must^be placed in a position by themselves. In the Iceberg period, 

 the Champlaiu, when the ice which covered the country was beginning 



