OLDER POTOMAC OF VIRGINIA AND MARYLAND. 555 



3. In 1895 (the month not stated on the label) Mr. Bibbins collected 4 more 

 of the cones, also for the Woman's College. 



4. Five specimens were collected by Mr. Bibbins for the Maryland State Geologi- 

 cal Survey, bearing the numbers of that survey, 8870, 887.3-8876. The first of these 

 bears also the date, 1895. The rest have no date, but are uniform with this in all 

 other respects, and were probably obtained at the same time. 



5. On August 31, 1896, Mr. Bibbins and Professor Ward made collections at 

 several points in this region, and 3 determinable specimens were collected on the 

 south side of the hill. It was near here, at a little higher level, that the same 

 party obtained on March 29, 1894, a nearly erect trunk which was silicified in the 

 interior above and lignitized on the exterior, while the lower end consisted entirely 

 of lignite and had been used in part for fuel. 



The iron rock at this locahty, hke the ferruginous sand rock of the 

 Tiptop mines above described, is sand impregnated with hmonite so as 

 to form a pretty firm rock. The material being coarse and without 

 cleavage is not suited for the preservation of fossil plants, and at the 

 same time the plants seem to have been floated for some distance and 

 roughly used. For these reasons the impressions are those of small 

 fragments that are in general not distinct. The conditions under which 

 they have been preserved have probably acted to exclude all forms that 

 are easily destroyed, and hence the species are fewer than they would 

 otherwise be and there is a great predominance of such as could endure. 



Some of the specimens can not be determined, but there are others 

 which can be made out. The following are all the species that can be 

 determined from Soper Hall, with the number of specimens of each : 



Atlii-otaxopsis expansa Font. « 3 specimens. 



Sequoia ambigua Heer 21 specimens. 



Sphenolepidium dentifolium Font. « 1 specimen. 



Sphenolepidium Sternbergianum densifolium Font 5 specimens. 



Sequoia ambigua Heer." 

 PI. CX, Fig. 13. 

 The most important fossils are cones in the form of mud casts, 21 of 

 which were found. These include all the cones of the first, second, and 

 third collections described above. They are more or less distorted, and 

 the plant matter had evidently in part been removed before the mud 

 took the casts. These cones are decidedly larger than the cones of 



« See p. 264. 



