GEOLOGICAL LITLRATURE OF THE VIRGINIA COASTAL PLAIN. 35 



Ward, L. F. Evidence of the Fossil Plants as to the Age of the 

 Potomac Formation. 



Amer. Jour. Sci., 3d ser., vol. xxxvi, pp. 119-131, 1888. Abstr. Nature, vol. 

 xxxviii, p. 462. 1888. 



The author concludes in regard to the Potomac formation that "if the stratigraphical 

 relations and the animal remains shall finally require its reference to the Jurassic, the 

 plants do not present any serious obstacle to such reference.'" 



1889 



Curtice, Cooper. Oriskanv Drift near Washington, D. C. 



Amer. Geol., vol. iii, pp. 223-225, 1889. 



The writer states that he found water-worn pebbles and cobbles near Alexandria and 

 Mt. Vernon carrying fossils of Oriskany age. Nine genera and eight species have been deter- 

 mined. The writer states that the cobbles come from the Potomac but it is not improbable 

 that they came from the Columbia deposits. They were transported from the region 

 beyond the Blue Ridge. 



Fontaine, William M. The Potomac or younger Mesozoic Flora. 



U. S. Geol. Survey, Monograph, vol. xv, pt. i, 377 pp.; pt. ii, 180 pis., Wash- 

 ington, 1889. 



The monograph contains a description of the Potomac deposits of Virginia In which 

 the lithologic characters of the deposits and their geographic occurrence are discussed 

 in considerable detail. Three hundred and sixty-five species of fossil plants, most of them 

 new, are described and figured. 



Knowlton, F. H. Fossil W^ood and Lignite of the Potomac Formation. 



Bull. U. S. Geol. Survey, No. 56, 72 pp., 7 pis., Washington, 1889. 



The author described the organic remains of the Potomac and their method of 

 occurrence and gives a detailed description of the microscopic appearance of five new 

 species of sllicified wood, four of which were obtained from the Potomac strata of 

 Virginia. 



The Fossil Wood and Lignites of the Potomac Formation. 



Amer. Geol.. vol. iii, pp. 99-106, 1889. 



After a careful microscopic examination of the sllicifled wood and lignite the author 

 concludes that all belong to the conifers. The cells of the lignite have been so much 

 distorted and metamorphosed that the specific determinations could not be made. The 

 sillclfled specimens are very perfectly preserved and belong to two genera Gupressinoxylon 

 with four species and Araucarioxylon with a single species. 



1890 



Clark, William B. Third Annual Geological Expedition into South- 

 ern Maryland and Virginia. 



Johns Hopkins Univ. Circulars, vol. x. No. 81, pp. 69-71. 



On the trip various localities along the Potomac, York, and .Tames rivers were visited 

 for the study of the Cretaceous, Tertiary, and Quaternary formations of the Coastal 

 Plain. Sections of the strata at Aquia Creek, Nomini Cliffs, Yorktown, and Grove Wharf 

 are given. 



