434 



Ferns were not very abundant as individuals, but diversified in type, 

 and represented by eight genera and fourteen forms. The conifers 

 appeared to have been an unimportant element. The only example 

 belonging to the Cycadaceae is the beautifully preserved small trunk now 

 referred to as Cycadeoidea. The monocotyledons were apparently not 

 an abundant element during the Cretaceous period, and the Laramie 

 flora is no exception. The dicotyledons were, of course, the most 

 abundant and diversified elements of this flora. 



Knowlton draws the following tentative conclusions as to the climatic 

 conditions under which the Laramie flora may have existed. It seems 

 to him beyond question that there must have been plenty of moisture on 

 account of the abundant presence of coal and the apparent requirements 

 of the majority of plants enumerated in his lists. It also appears to him 

 a natural conclusion that the climate was warm, at least warm temperate. 



Knowlton dwells at length upon the geologic relations of the flora, 

 a feature which makes his paper particularly interesting for the geologist. 

 He compares the Laramie flora with the Montana flora, Denver forma- 

 tion, Arapahoe formation. Lance formation, uppermost Cretaceous of 

 the Atlantic Coastal Plain, Patoot Series of Greenland, and the Upper 

 Cretaceous of Europe. 



A. C. N. 



Mineralogy of Pennsylvania. By Samuel G. Gordon. Special 



Publication No. i, Academy of Natural Sciences, Philadelphia, 



1922. Pp. 255, pi. I, figs. no. 



Pennsylvania's mineral localities have been combed by generations 



of enthusiastic specimen hunters until there is scarcely a large collection 



anywhere in the world that does not include representatives from some 



of the famous localities of the state: Falls of French Creek, Wood's 



Chrome Mine, the Gap Nickel Mines, or the old lead mines of Phoenix- 



ville. The Pennsylvania Piedmont, with its great variety of rock types 



crowded into a small triangle in easy reach of Philadelphia, furnished a 



readily accessible collecting groimd at the period when mineralogy was 



