OLDER POTOMAC OF VIRGINIA AND MARYLAND. 565 



their insertions on the midrib. The tertiary nervation can not be dis- 

 tinctly seen. 



The specimen on which this imprint occurs constitutes collection 

 No. 2. The rock matter carrying the plant is identical with that from 

 Jackson street, which contains Acrostichopteris longipennis, and no doubt 

 the stratum yielding both the species is the same. 



This species is named for its discoverer, Prof. P. R. Uhler. The 

 specimen is deposited in the National Museum. 



Thyrsopteris Meekiana Fontaine. 



PI. CXIX, Fig. L 



1SS9. Thyrsopteris Meekiana Font.: Potomac Flora (Monogr. U. S. Geol. Surv., 

 Vol. XV), p. 125, pi. xxxviii, figs. 2, 2a, 2b, 3, 3a, 4, 4a, 8; pi. 1, figs. 7, 

 7a, 8; pi. fi, figs. 3, 3a. 



This species is shown in one good specimen from the Terra Cotta 

 Works, collection No. 6. It is described in Monograph XV as one of the 

 most abundant plants collected by Professor Meek at an unknown 

 locality in Baltimore. This specimen, shown in PI. CXIX, Fig. 1, is the 

 terminal part of a penultimate pinna with a good many ultimate ones 

 bearing pinnules. It gives a part of the fern not shown in any of the 

 specimens figured in Monograph XV. This fossil shows that in the 

 fern, toward the summit of the compound pinnae, the pinnules lose their 

 lobing and become entire, passing finally into teeth, while the ultimate 

 pinnae become dentate pinnules. The upper portions of the pinnules, 

 after the loss of their lobing, look somewhat like a small Cladophlebis. 

 This species, while it is most abundant in the Baltimore strata, is found 

 also in the beds of the Rappahannock horizon of Virginia. The specimen 

 bears the number 5358 of the museum of the Woman's College of Balti- 

 more. 



ViTiPHYLLUM MULTiFiDUM Fontaine." 



PL CXIX, Figs. 2-4. 



Vitiphyllum multiUdum was first described in Monograph XV from 

 Belt and Covington streets, Baltimore. It is much the most common 

 plant in the recent collections from Federal Hill, which contain no fewer 



a See p. 553. 



