Maeyland Geological Survey 151 



the year. The Patuxent and Arundel floras may be compared with cer- 

 tain modem temperate rain-forests made up of a dense growth of ferns 

 and cycads in more or less pure stands, with occasional conifers towering 

 above the general level of the vegetation, which was relatively low, and 

 gradually predominating in passing from the coast to the uplands. 



The Potomac floras, which are the most extensive known floras from 

 the Lower Cretaceous and only rivalled by those from Portugal, serve 

 admirably to indicate the progression of the plant world during the 

 Lower Cretaceous. 



Omitting certain forms from the Virginia area which have not yet been 

 studied and which do not materially alter the proportions, and excluding 

 doubtful species like those of Carpolithus and other indefinite genera, 

 we find about 100 species in the Patuxent flora. These include 36 

 species of ferns, 2 equisetums, 29 cycadophytes, 1 Baiera, 24 conifers, 

 19 of which belong to the Pinacese, and the remainder to the 

 Taxacese, and 6 altogether doubtful angiosperms. The Arundel flora is 

 only one-third as extensive as the Patuxent and contains but 10 species 

 of ferns, 5 cycadophytes, 13 conifers, including 10 in the Pinacese, and 

 3 in the Taxacese, and 5 questionable angiosperms. The Patapsco flora, 

 which is about the same size as that of the Patuxent, contains 23 ferns, 

 the same two equisetums as the Patuxent, 10 cycadophytes, 17 conifers, 

 including 14 Pinacese and 3 Taxacese, and about 25 angiosperms, most of 

 which are reliably determined. 



