430 OLDER MESOZOIC FLORAS OF UNITED STATES. 
Pennsylvania. The splendid variety, C. grandifolium Storrsii, from 
Oroville, shows that this form only underwent certain modifications 
in passing from the Trias to the Jura, and its exclusively American 
character gives it great value as an index to plant evolution on this 
continent in Older Mesozoic time. 
As all the other columns of the table represent the Newark system, 
which is believed to constitute a geological unit from Massachusetts 
to North Carolina, little interest attaches to the discovery of forms 
common to the several areas. A large number are found in both the 
Richmond and the North Carolina coal fields, which was, of course, to be 
expected, and the rediscovery of the Emmons types has done much to 
demonstrate the stratigraphical identity of these coal fields. Mr. Wan- 
ner’s excellent work in Pennsylvania has tended to bring the deposits 
of York County, Pennsylvania, into substantial harmony with those 
farther south. The material from the Connecticut Valley and from 
New Jersey is as yet too meager to make a full comparison possible, 
and it seems altogether probable that, even on the assumption of 
identity of age and aside from differences due to geographical dis- 
tribution, the element of climate may have had some effect in causing the 
northern and southern areas to differ in their flora in Mesozoic time. 
