PLANT LOCALITIES. 21 



very few other species have been fomul. A small llnleropsis occurs next in 

 abundance. It is not found at the mile-post, but has most resemblance to a 

 plant occurring at Federal Hill, in Baltimore. The o-reat number of im- 

 pression.s of Sapindopsis is surprisinfj-, as is also the fact that so many of the 

 imprints show the preservation of the same portions ; i. e., the terminal part 

 of the pinnate leaf 



Two or three imprints of bivalve shells were found. These appear to 

 be small Uuios, and they resemble some of the Wealden Unios figured in 

 Dunker's "Monograph of the Wealden.'" This spot will be referred to as 

 "Bank near Brooke." The clay carrying the fossils seems to be a remnant 

 of an original stratum of considerable extent. It is comparable to the lower 

 Potomac clay over the sand in Baltimore. 



Going north, the ne.xt plant locality was seen at Mr. Kankev's farm, on 

 Neabsco Run. It lies three-fourths of a mile west of the Telegraph road 

 and nearly opposite the place where the road crosses the run at Mr. Kankey's 

 house. This is near the western margin of the Potomac area. Only six 

 or eight feet of Potomac sand and cla}' can be seen, and the floor of Azoic 

 slate is visible in several places. The sand is of the usual kind. The clay 

 that carries the fo.ssils is dark gray and very tenacious, and it is undisturbed;, 

 but it lies in irregular patches of limited extent. Very few species occur 

 liere. Diomitcs Buchianus is the ordy plant of imiwrtance. Great numbers 

 of its leaves occur in some i)ortions of the clay, so that they are matted 

 together. Here, as at Dutch Gap, this plant, when ver}- abundant in a clay, 

 seems to exclude other species. It is noteworthy that in going north from 

 Dutch Gap this is the iirst locality where any trace of this plant occurs, and 

 the great number of the specimens seen at its reappearance is remarkable. 



This locality deserves especial notice for the lignite found there. It 

 occurs precisely as at Potomac Run, evidently originating in the same way; 

 i. e., by the prostration of a forest of coniferous trees and their subsequent 

 change to lignite in the place where they grew. The lignite is exposed 

 along the channel of a small stream for some thirty or forty yards. The 

 stream has very feeble erosive power, and the deposit of lignite is probably 

 not full}' shown. 



'These have been since determined by Dr. White to be Eatlteria. 



