1912.] NATURAL SCIENCES OF PHILADELPHIA. 371 



published the exact localities from which it had been obtained, but 

 it may have been identical with the species here characterized, 

 although in the writer's opinion this is more like C. lindleyanum 

 (Witham) Kraus. Both of these species had been described from 

 the Lias of England, and Rogers accordingly inferred the Jurassic 

 age of the American rocks, but there can be no question that our 

 form is really entirely distinct from either, and it is named after the 

 State in which it was discovered. 



The distribution of these species is shown in the following table; 

 material from localities M. 2 and M. 3 could not be obtained for 

 study. 



Locality B. 123456789 10 

 A. virginianum X X 



A. vanartsdaleni X X X X X X X X X X 



B. pennsylvanianum X X X 



Locality M. 1 2 3 C.l 2 L.l 2 3 Y.l 



A. virginianum 



A. vanartsdaleni X — X X X X X 



B. 'pennsylvanianum X X 



In conclusion, a word may be added concerning the bearing of the 

 fossil wood on the question as to the climate of the Triassic. A 

 prevailing red color in the sediment of any period has now come to be 

 recognized by geologists as an indication that the climate of the 

 time was to some extent arid. The obscurity of the annual ring in 

 these trees may be regarded as pointing to a certain extent 9 in the 

 same direction, for it shows that there could not have been any 

 marked seasonal variation in temperature conditions, and the sim- 

 plest way in which this could occur would be under the prevalence 

 of a dry climate, caused perhaps by some peculiarity of configuration 

 of continents or elevation of mountains, which produced a different 

 circulation of the atmosphere from that prevailing here at present. 



The arkosic matrix of the wood specimens (from the feldspar of 

 which their silica has been derived) is also suggestive of the same 

 state of affairs, for it must have been formed under conditions where 

 disintegration exceeded decomposition, so that the feldspar and 

 other silicates could be broken up without extensive chemical altera- 

 tion, and although this could result equally well in frigid as in arid 

 climates, there is no direct evidence for the former, so that the 



9 Although the value of this evidence is limited by the fact that living arau- 

 carias show little annual ring, even though growing in temperate climates. 



