76 



PHYSIOGRAPHY AXD GEOLOGY OF THE COASTAL PLAIN PROVINCE. 



Below this exposure a short distance the crystallines show along the 

 right bank and they are also exposed in the bed of a small stream which 

 flows into the left bank about one and a half miles above Dutch Gap canal, 

 these limited outcrops constituting the most easterly appearance of the 

 Piedmont rocks in this area. 



For about two miles before reaching Dutch Gap canal low exposures of 

 the Patuxent formation overlain by a considerable thickness of Pleistocene 

 are exposed along the left bank. The materials are grayish arkosic, cross- 

 bedded sands with numerous clay lenses, some of which have yielded fossil 

 plants, notably a low exposure about one mile above the canal where the 

 following species have been collected : 



Abietites lungifolius (Font.) Berry 

 Ahietites foliosus (Font.) Berry 

 Abietites macrocarpus Font. 

 Acrosiichoptei is pliii ipartita (Font.) 



Berry 

 AcrostichopI oris cyclopteroides Font. 

 Acrostichopteris parrifolia Font. 

 Baiera foliosa Font. 

 Carpolithus virginioisis Font. 

 Carpolithus geminafus Font. 

 Carpolithus latiis Font. . 

 Carpolithus sessilis Font. 

 Ceptalotaxopsis brerifolia Font. 

 (Jephalotaxopsis magiiifulia Font. 

 Cladophlebis virginiensis Font. 

 Cladophlebis distans Font. 

 Cladophlebis Browniana (Dunk.) Seward. 

 Cladophlebis Ungeri (Dunk.) Ward. 

 Cladophlebis Albert sii (Dunk.) Brongn. 

 Cladophlebis oblongifolia Font. 

 (Cladophlebis sphenopteroides Font. 

 Cycadeospernum eUiptiviim Font. 

 Dioonites Buchianus (Ett.) Born. 

 Equisetum Burchardti (Dunk.) Brongn. 

 Equisetum Lyelli Mant. 

 Ficophyllum crassinerve Font. 



Gleiclirnia nordenskioldi Heer 

 Xageiopsis longifoUa. Font. 

 Nageiopsis zamioides Font. 

 Onychiopsis Ooepperti (Schenk) Berry 

 Phyllooladopsis hcterophylla Font. 

 I'odozamites aculifolius Font. 

 Proteaephyllum tcnuinerve Font. 

 Rogersia longifoUa Font. 

 Ruffordia acrodentata ( Font. ) Berry 

 Ruffordia Goepperti (Dunk.) Seward. 

 l^clcroptcris elliptica Font. 

 Splienolcpis Kurriana (Dunk.) Schenk 

 Siequoia ambigua Heor 

 Sequoia delicatiila Font. 

 Thinnfehlia gramdata Font. 

 Thyrsopteris brevipcnnis Font. 

 Thyrsopteris divarieata Font. 

 Thyrsopteris meelciana Font. 

 Thyrsopteria angustifolia Font. 

 Thyrsopteris angustiloba Font. 

 Thyrsopteris nana Font. 

 Thyrsopteris ineaqvApinnata Font. 

 M'illiamsonia virginiensis Font. 

 Zamites crassinervis Font. 

 Zamites tennuinervis Font. 



Dutch Gap canal, celebrated historically, is 17 miles below Eich- 

 mond. It is only about 100 yards in length and cuts off an oxbow of seven 

 miles. Low exposures of Patuxent materials are equally well exposed in 

 both banks and show in the following section, the following figures being 

 a diagrammatic representation of the east bank. 



