256 THE POTOMAC OE YOUNGER MESOZOIC FLORA. 



runs with an undulating dip beneath the raih'oad track, exposing some five 

 or six feet of length. The clay is very fine, unmixed with sand, and fairly 

 well laminated. In this the leaf imprints occur beautifully preserved. 

 Unfortunately but a few feet in length of this substance was found. 



Taxod'mm Brookense is in many features a good deal like the plant 

 which Velenovsky calls Widdringtoma- BeicJdi, and of which he gives 

 figures representing an enlarged twig closely resembling some of the forms 

 of the Potomac fossil, especially in the shape of the leaves and in the 

 lancet shaped tips of the facial ones. His description in many points will 

 apply to the Potomac plant. The older stems, such as the one given in 

 PI. VIII, Fig. 6, depart more widely from the Potomac forms. 



On the whole the twigs of the Potomac plant are stouter and more 

 rigid than those of W. Beichii. Possibly the Potomac fossil is an ancestral 

 form of the Bohemian plant. Heer describes a fossil fi'om the Atane beds 

 of Greenland similar to the Bohemian fossil, but says its leaves have no 

 midrib. As stated, it is not easy in all cases in T. Brookense to detect the 

 midnerve, and Heer may have had specimens in which it was not pre- 

 served, although originally present. Velenovsky does not show that the 

 Widdringtonia like cone which he assigns to his plant is certainly con- 

 nected with it. The shape and the arrangement of the leaves of T. 

 Brookense are strikingly like what may be seen in the young leaves of 

 Glyptostrohiis pendulus Endlicher. 



Taxodium (Glyptostrobus) Brookense, var. angustifolium, sp. nov. 



Plate CLXVII, Fig. 1. 



Copiously branched, with very slender twigs ; leaves very narrow, 

 linear, closely appressed, obtuse to subacute; ultimate twigs cord-like, 

 and going off^ irregularly from the penultimate ones; nerves very slender 

 and thread-like. 



Locality: White House Bluff". 



This plant in essentials is the same as the noi'mal T. Brookense, but it 

 is uniformly more slender, the leaves are narrower and always close 

 appressed, and it has a more irregular mode of branching, with more 



'Die Gymnospermen der bohmisch. Kreideformation, PL VIII, Figs. 4-G, 16; PI. X, Figs. 1, 11, 

 12; PI. VIII, Fig. 16. 



