DEbCKlPTlON OF THE SPECIES. 291 



and petiole extremely thick proportionally : lateral or primary nerves pro- 

 portionally and in most of the forms absolutely slender, extremely irregular 

 in arrangement, forming a lax reticulation of very archaic type. Ultimate 

 reticulation strongly marked and fern-like. 



This genus is an important one in the Potomac flora, and has con- 

 tributed a considerable number of individuals to the vegetation of that 

 opocli. It is largely developed in association with Jurassic types of plants, 

 as at Fredericksburg, where it is most abundant, and is almost wanting in 

 the strata where more modern elements abound, as at Brooke, White 

 House, and Baltimore. As illusti-ating the archaic and peculiar features of 

 these leaves and those of J'roteirpJii/Uum, I may state that for some time 

 no other leaves but these were found at Fredericksburg, and finding them 

 associated only with plants of Jurassic facies I found it difficult to give 

 any good characters distinguishing them from ferns. There is a general 

 and strong resemblance between these plants and some species of Ficus, 

 and for this reason it seems best to place them in a new genus, indicating 

 by its name the apparent affinity with that genus. It is quite possil)le that 

 these ai-e ancestral forms of Ficus. 



FlCOPIIYLLl'M CRASSINERVE, sp. nOV. 



Plato CXLIV, FiR. 3; Pl.ate CXLV, Fig. 3; Plate C.XLVI, Fig. 1 ; Pliite CXLVII, Fig. 4; Pl.ate 

 CXLVIII, Figs. 1, 2, 4; Plate CLVII, Fig. 4; Plate CLXXIIl, Fig. 10. 



Leaves lai'ge, of varying size, sometimes attaining very large dimen- 

 sions, elliptical in outline, subacute, with tips often broadly wedge-shaped, 

 I'ounded off gradually at base, and narrowed slowly into the petiole. Mid- 

 rib very stout, woody, and strong neai-ly to the tip of the leaf, rather 

 vaguely defined, and apparently somewhat succulent; primary nerves in 

 proportion to the mid-rib slender, but compared with those of the otlier 

 species of the genus thick ; the}^ go off on each side of the midrib, mostly 

 very obliquely, subopposite or alternate, arch backwards and then strongly 

 forwards, curving around so as to connect with the next nerves of the same 

 rank ; they send off on the outer side branches which continue for some 

 distance curving towards the summit and gradually approaching the 

 margin ; between tlie main lateral nerves, which are usually thick and 

 strongly marked, subordinate lateral ones are commonly sliown, as in PI. 



