FOSSIL FERNS. LONCHOPTERIS. 119 
a strong midrib, which extends to the apex ; veins simple, 
or once or twice dichotomous, proceeding almost at right 
angles from the median vein. 
This genus embraces a very large proportion of the ferns 
which have contributed to the formation of the coal, and 
whose leaves and stems are preserved in the associated 
strata. The originals of many species were undoubtedly 
arborescent, and attained a large size ; some leaves four feet 
wide, and of a proportionate length, have been observed. 
More than one hundred species are determined. An Ame- 
rican species (Pecopteris Sillimant) is figured in illustration 
of certain botanical terms, Lign. 16, ante, p.110. Several 
species of Pecopteris occur in the fluvio-marine oolitic de- 
posits near Scarborough, and leaves in fructification are not 
uncommon: jig. 1, Lign. 27, represents a leaflet slightly 
magnified 
AM 
WSS 
Lien. 28. LoncnortTeris MANTELLI. 
Wealden, Tilgate Forest. 
Fig. 1 and 2.—Leaflets magnified, to show the reticulated venation. 
3.—A fragment of a frond; nat. 
Loncnopreris (spear-leafed.) Lign, 28.—Leaves many 
times pinnated ; leaflets more or less adherent to each other at 
their base, traversed by a midrib ; secondary veins reticulated. 
The three known species which compose this genus resemble 
