22 THE POTOMAC OR YOUNGER MESOZOIC FLORA. 



This lignite exhibits exactly the same physical cliaracter as that on 

 Potomac Run, having the curious mingling of features of jet and true lig- 

 nite with woody structure. Some of the trees, whicli appear to have been 

 three feet in diameter, are much flattened, having evidently been subjected 

 to great pressure. As only a few feet of material now covers these trunks, 

 the Potomac here must have lost largely by erosion. The locality will be 

 referred to as "Kankey's on Neabsco Run." 



Where the Coast Line Railroad crosses Occoquan River a long cut of 

 considerable depth has been made to form the approach on the south side to 

 the bridge. This cut shows Potomac sand, with fossiliferous reddish and 

 gray clay in small irregular patches. In some places the floor of Azoic slate 

 is shown, so that here, as well as at Kankey's, the base of the Potomac is all 

 that remains. The only fossil worth mentioning that occurs here is Dio- 

 diiites Bucliianus. It is by no means so abundant as at Kankey's, and in 

 general the plants are very rare and fragmentary. No collection was made. 



The next locality which has afforded specimens is a little south of Tel- 

 egraph Station. This station is on the Coast Line Railroad, three miles 

 north of the crossing over Occoquan River. A series of cuts made in the 

 Potomac sand and clay are found between the station and the river. The 

 only spot in this region at which plant-impressions have been found is in 

 a cut about one and a half miles south of the station, and towards the river. 

 The material exposed is Azoic slate, with Potomac sand and clay resting on 

 it. The clay containing plants is mostlv disturljed and colored gray. This 

 has poor impressions, but in the left-hand side of the cut looking north is a 

 pocket of rather sandy, laminated, and reddish clay, which has afforded a 

 number of well-preserved impressions. The most important of the plants 

 Jiere is Dioijnitcs Bucliianus. This is the farthest point north at which good 

 specimens of this fossil have been obtained. Fragments of it occur at Fort 

 Washington and also at Baltimore, but they are few and small. A number 

 of ferns, conifers, etc., occur here, giving a group of plants much like those 

 found at Dutch Gap. The locality will be referred to as " Near Tele- 

 graph Station." 



White House Bluff" is the end of a point which terminates on the Po- 

 tomac about two miles below Mount Vernon. The bluff' begins just below 



