Till; flora ok Till: C0A1 FORMATION. 117 



meantime the principal genera, of which representatives have been 

 found in Acadia, are the following (Figs. 166, 167, and Figs. 69 to 

 72):— 



1. Cyclopteris, Brongn. — Leaflets more or less rounded, or wedge- 

 shaped, without midrib, the nerves spreading from the point of at- 

 tachment. This group includes a great variety of fronds evidently of 

 different genera, were their fructification known ; and some of them 

 probably portions of fronds, the other parts of which may be in the 

 next genus. 



2. Neuropteris, Brongn. — Fronds pinnated, and with the leaflets 

 narrowed at the base ; midrib often not distinct, and disappearing 

 toward the apex. Nervures equal, and rising at an acute angle. 

 Ferns of this type are among the most abundant in the Coal formation. 



3. Odontopteris, Brongn. — In these the frond is pinnate, and the 

 leaflets are attached by their whole base, with the nerves either pro- 

 ceeding wholly from the base, or in part from an indistinct midrib, 

 which soon divides into nervures. 



4. Dictyoptcris, Gutbier. — This is a beautiful style of fern, withleaflets 

 resembling those of Neuropteris, but the veins arranged in a network 

 of oval spaces. Only one species is known in our Coal formation. 



5. Lonchopteris, Brongn. — Ferns with netted veins like the above, 

 but with a distinct midrib, and the leaflets attached by the whole base. 

 Of this also we can boast but a single species. 



6. Sphenopteris, Brongn. — These are elegant ferns, very numerous 

 in species, and most difficult to discriminate. Their most distinctive 

 characters are leaflets narrowed at the base, often lobed, and with 

 nervures dividing in a pinnate manner from the base. 



7. Phylhptcris, Brongn. — These are pinnate, with long lanceolate 

 pinnules, having a strong and well defined midrib, and nerves pro- 

 ceeding from it very obliquely, and dividing as they proceed toward 

 the margin. The ferns of this genus are for the most part found in 

 formations more recent than the Carboniferous ; but I have referred to 

 it, with some doubt, one of our 'species. 



8. Alethopteris, Brongn. — This genus includes many of the most 

 common Coal formation ferns, especially the ubiquitous A. lonchitiea, 

 which seems to have been the common brake of the Coal formation, 

 corresponding to Pteris aquilina in modern Europe and America. 

 These are brake-like ferns, pinnate, with leaflets often long and narrow, 

 decurrent on the petiole, adherent by their whole base, and united at 

 base to each other. The midrib is continuous to the point, and the 

 nervures run off from it nearly at right angles. In some of these ferns 

 the fructification is known to have been marginal, as in Pteris. 



