558 MESOZOIC FLORAS OF UNITED STATES. 



Thyrsopteris rarinervis Font 1 specimen. 



Vitiphyllum multifidum Font 150 specimens. 



Vitiphj^lum parvifolium Font ,7 specimens. 



Ament of conifer (b) Font 1 specimen. 



AcROSTicHOPTERis PARviFOLiA Fontaine. 



PL CXVI, Fig. 5. 



1889. Acrostichopteris parvifolia Font. : Potomac Flora (Monogr. U. S. Geol. Surv., 

 Vol. XV), p. 108, pi. xciv, figs. 5, 5a, 9, 9a, 10. 10a, 12, 12a; pi. cLxxi, figs. 

 3, 3a, 4, 4a; pi. clxxii, fig. 14. 



This species, although not so common as ^-i. longipennis, is one 

 of the more abundant fossils, 19 specimens being found. As will be 

 gathered from the description of it given in Monograph XV, it is most 

 abundant in the lower strata of the Lower Potomac of Virginia. Like 

 A. longipennis the specimens are mostly fragmentary. A few of them, 

 however, are more complete than any in the Virginia specimens. PI. 

 CXVI, Fig. 5, gives one of the best of these. It occurs in collection 

 A^o. 5 and bears the number 5959 of the museum of the Women's College 

 of Baltimore. 



Adiantites parvifolius Fontaine n. sp. 



PI. CXVII, Fig. 1. 



In collection No. 5 is found a single specimen of what seems to be 

 a species of fern not hitherto described from the Lower Potomac. It 

 resembles somewhat Thyrsopteris brevipennis Font., from the Lower 

 Potomac of Virginia. Unfortunately not enough of it has been found 

 to enable one to make out its full character. It is well known that 

 the foliage of ferns varies much in the different parts of the same frond, 

 and the material possessed may give a very incomplete idea of the 

 plant. It is a fragment of a penultimate pinna. It carries several 

 ultimate pinnse, which mostly have the tips wanting. These pinnae 

 are short and indicate that the plant was of small dimensions. The 

 pinnules are small and rounded in shape or broadly elliptical. They 

 are narrowed to the base by which they are attached. Each pinnule 

 has a parent nerve which enters its base and splits up into a number 

 of forking branches. These diverge flabellatelj^ to fill the lamina. PL 

 CXVII, Fig. 1, represents the specimen which bears no number. 



