88 PP. REPOET OF PROGRESS. FONTAINE & WHITE. 



that of the Conglomerate group, this is one of the most 

 abundant forms, forming almost the entire flora, as in the 

 Sharon Coal of the Conglomerate of Pennsylvania. In 

 species in the npper strata we have to note a total change 

 of facies from the coarse large forms with strong and s]3ar- 

 ingly forked nerves found at lower horizons, to the type 

 which approaches close to Callipteridium in nervation, 

 while it is more slender, and shows a tendency to hetero- 

 morphism. 



AletJiopterisVirginiana, Sp. nov., PL XXXII, Figs. 1-5. 

 PL XXXIII, Figs. 1-4. 



(Frond, tripinnate ; primary rachis strong and rough ; 

 primary pinnae triangular in outline, and tapering rapidly 

 to the summit ; secondary pinnae, opposite or alternate, 

 going off at nearly a right angle, long and tapering slowly, 

 with a large and rather rigid rachis ; pinnides, alternate, 

 separate below but united above, and becoming more so as 

 we approach the summit of the primary pinnse where the 

 pinnules have all united, and the ultimate pinnse are re- 

 duced to long, undulate or lobed pinnules, which finally 

 pass into simple pinnules of the normal kind ; the pinnules 

 also coalesce towards the ends of the ultimate pinnse, and 

 are often swollen at the base, as if by two sori, placed one 

 on each side of the mid-nerve at the base, as showm in Fig. 

 1, PL XXXIII ; mid-nerve well marked, and extending to 

 the apex ; lateral nerves numerous, closely placed, going off 

 nearly at right angles with the mid-nerve. Very fine, fork- 

 ing once normally, or with one of the branches, (occasionally 

 both) again forking, simple nerves occasionally interspersed, 

 all proceeding nearly parallel to each other to the margin; 

 lowest pinnule on each side of the base of the pinna, 

 of the ultimate order, heteromorphoas by having the lower 

 side of the pinnule lobed while the upper side is entire.) 



Fig. 2, PL XXXIII, shows a form from the lower part 

 of the plant, where the pinnules have a tendency to become 

 lobed ; and Fig. 2 shows this lobing in a more decided 

 manner, thus causing the plant to tend to a quadripinnat- 

 ilid character. 



