CLADOPHLEBIS. 93 
Srigida, Heer, the pinnules of which are longer, stiffer, and less 
falcate. 
Fontaine does not include Cladophlebis Albertsii (Dunk.) among 
the Potomac plants, but some of the pinne which he figures 
strongly resemble this species. As in the case of Z’hyrsopteris, there 
appear to be some exceedingly narrow and ill-defined differences 
between certain species. In sterile fronds of a type similar to 
those of C. Albertsii it is hardly possible to determine the specific 
limitations with any certainty; possibly no form of frond is so 
widely distributed in Jurassic and Lower Cretaceous rocks in all 
parts of the world. 
C. virginiensis, Font.,? possesses pinnules a trifle broader and 
shorter than those of C. Albertsci, and with entire margins. In 
C. denticulata, Font.,° there is a very distinct resemblance to C. 
Albertsii, but the fragments on which the species is founded are 
too small to enable us to form an opinion as to the frond as a 
whole. 
C. faleata, Font.,* is another fern of very similar form, but it 
suggests a larger frond than that of C. Albertsii and differs in the 
lobed margins of some pinnules; it is difficult to separate some 
of the figures of C. virginiensis, Font., from those of C. falcata, 
Font. In describing the former species Fontaine remarks that 
“‘The Potomac plant is strikingly like Brongniart’s Pecopteris 
Whitbiensis and P. tenuis, and one may well hesitate to separate 
them.’’° There is also the following remark with reference to the 
same species which might be applied, in principle, to other ferns 
from the Potomac beds:—‘‘It does not, however, seem proper to 
make the Potomac plant an <Asplenium so long as it shows no 
fructification.”” Another species, C. acuta, Font.,° has the same 
type of frond as C. Albertsdi and other ferns; it is spoken of as 
‘more like Dunker’s Neuropteris Albertsii . .. . than any other 
previously described fossil, and is no doubt quite near the Wealden 
species.’”’ The same species is compared also to Heer’s Pteris 
Albertsii and Schenk’s Alethopteris Albertsii. The resemblance 
1 Abh. k. béhm. Ges. Wiss. math.-nat. Cl. vol. ii. Folg. 7, 1888. 
2 Potomac Flora, p. 70, pl. iii. figs. 3-8 ; pl. iv. figs. 1 and 3-6. 
3 Ibid. p. 71, pl. iv. fig. 2; pl. vii. fig. 7. 
4 Ibid. p. 72, pl. iv. fig. 8; pl. v. figs. 1-6, etc. 
5 Ibid. p. 71. 
6 Tbid. p. 74, pl. v. fig. 7; pl. vii. fig. 6, etc. 
