Maryland Geological Survey 71 



seen in some of the later formations, and particularly the Magothy for- 

 mation along the line of the Chesapeake and Delaware Canal, suggest the 

 possibility of actual folding in the Patapsco and earlier formations. 



Organic Eemains. — The Patapsco deposits have yielded a few speci- 

 mens of poorly preserved unios and an extensive flora, including repre- 

 sentatives of the Pteridophyta, Cycadophytae, Gymnospermie, and 

 Angiospermse. The ferns, cycads, and conifers represent for the 

 most part the dwindling remnants of the Patuxent-Arundel flora, some 

 species being common to all three formations and the genera being 

 largely identical. The fern genera Scleropteris, Schizceopsis and Tceni- 

 opteris have disappeared, but Ruffordia, Cladoplilebis, and Onychiopsis 

 are still common. Petrified remains of a species of Tempslcya and im- 

 pressions of fronds of a peculiar new genus of ferns, Knowltonella, are 

 highly characteristic of this formation. Among the cycads Podozamites 

 and Zamites are represented, but the genera Nilsonia, Dioonites, Ctenis, 

 Ctenopteris, and Ctenopsis have disappeared. Silicified trunks of Cyca- 

 deoidea have been found in the Patapsco, but it is questionable if they 

 have not been reworked from the older formations. 



Among the gymnosperms Laricopsis, Baiera, Geplialotaxopsis, and 

 Arthrotaxopsis are no longer represented. Species of Widdringtonites 

 and Pinus are new and characteristic, while the genera Sequoia, Spheno- 

 lepiSj Brachypliyllum, and Nageiopsis are still present. 



The marked distinctness and more modern aspect of the Patapsco 

 flora is due, however, to the abundance of Dicotyledonse, which fore- 

 shadow and were undoubtedly for the most part ancestral to the Dicotyled- 

 onse of the Upper Cretaceous Earitan formation. 



The more characteristic of these are the various species of AraJia- 

 epTiyllum, Sterculia, Cissites, Celastrophyllum, Populophyllum, etc. The 

 compound leaves of Sapindopsis are one of the most striking dicotyledo- 

 nous elements present. Three species are known and all are strictly 

 confined to this horizon. 



