Sinnott and Bartlett — Coniferous Woods. 277 



and Florida Avenue exposed several plant beds, and a deposit 

 of blue clay which contained a great deal of lignite in the form 

 of prostrate logs and branches. The lignite at this locality had 

 the appearance of an accumulation of drift wood ; there were 

 no leaf impressions directly associated with it. 



On account of the very irregular bedding of the Potomac 

 strata it is quite useless to attempt to generalize a section even 

 for so small an area as the Central High School locality. The 

 excavation was made on a somewhat steep slope and was ter- 

 raced so that the entire section could not be seen from any one 

 point. At the highest elevation on the site (alt. 183'5 ft.) the 

 section was as follows : 



"Lafayette." Reddish loam 2 ft. 



Yellowish gravelly loam 4 ft. 



Patuxent. Varicolored unstratified clay 11*5 ft. 



White clay (below 1G6 ft.) ? 



The face of the next terrace (beginning at alt. 166 ft.) gave 

 the following section : 



Patuxent. Varicolored clay *5 f t. 



White clay, grading to blue, con- 

 taining lignite at base 14*5 ft. 



A few feet away the section was continued (below 151 ft. 

 alt.) as follows : 



Patuxent. Blue lignitic clay 1ft. 



Ferrugineous sand .. 3 ft. 



White and colored arkosic sand. 7 ft. + 



At another point in the excavation the white arkosic sand, 

 continuous with that at 140 ft. in the base of the above sec- 

 tion, had a depth of 20 ft. and rested upon a thin continuous 

 laminated layer (varying from less than an inch to 3 ft. in 

 thickness) of light brown or pinkish clay, exceedingly rich in 

 leaf impressions. From this layer the following forms were 

 identified : 



Pteridophyta 



Acrostichopteris pluvipartita (Fontaine) Berry 



(Abundant and characteristic. Known only from the 

 Patuxent formation.) 

 Dryopterites virginica (Fontaine) Berry 



(One specimen. Heretofore known with certainty only 

 from the Patuxent formation near Fredericksburg, Vir- 

 ginia.) 

 Onychiopsis Goepperti (Schenk) Berry 



(Very abundant and variable.) 

 Onychiopsis latiloba (Fontaine) Berry 

 Onychiop>sis psilotoides (Stokes & Webb) Ward 



