Pitre - eee 
LL Lesquereux on the Coal Formations of N. America, 381 
leafed Sphenopteridee, the Odontopteridee belong to coal No. 1 
with most of the fruits of the coal measures; the Newropteridea, 
the Pecopteridee and a peculiar section of small leafed Sphenopte- 
ride belong to coals No. 8 and 4. 
As if to show how useless it would be to argue on the distri- 
bution of the coal-flora as resulting from successive variations of 
species and of genera, we find predominant genera represented in 
the whole thickness and in the whole extent of the coal-fields by 
species so variable that they can be called polymorphous, and 
which nevertheless preserve everywhere their identity. Thus 
appear Newropteris hirsuta Lsqx., N. flecuosa Bret., Pecopieris poly- 
morpha Brgt. In the paleontological report of the Pennsylvania 
geological survey, I have figured eighteen formsof the first of these 
species, passing by insensible transitions from a small round leaflet 
to a large, nearly square Cyclopteris ; then to cordate or reniform 
leaf of medium size; then to opposite, oval-lanceolate leaflets 
united by a narrow margin; then to a digitate leaf of which the 
five divisions are lanceolate-obtuse, and thus ad infinitum. Nev- 
ertheless, this species is perfectly well characterized and may be 
identified at first sight in any of its multiple forms.* 
There is not in the number of Neuropteridece and Pecopieridece 
a well characterized species which could be admitted as a modi- 
lied form of the predominant and variable species. Moreover, 
the numerous species of Newropteris and Pecopleris appear at 
coal No. 8 and 4 in the middle of the coal-measures, an do 
not ascend higher, while those species which should be gig 9 
ered as originators or parents an aged ace! ought to be de- 
stroyed (from the law of selection) by their offspring, continue 
to predominate to the top of the coal-measures. hus the oe: 
tation of the coal shows at different geological horizons, both a 
form between the lost types and the following ones. The large- 
No. 1B 
culiar types, without regard to the former or extinct ones, one 
& continual reappearance in the whole thickness of the coal- 
measures of well-established species which neither by their “esa 
or their nature appear particular] prepared to vig — 
Varying the successive changes W ich have acted on the surface 
of the coal-measures at the time of their formation. . 
It is certainly possible to suppose that some pte apets - 
Mersion, or upheaval of the coal-marshes, has modified their 
. in simple leaflets detached from the stem, 
and neve rere no ce ti ei in its varieties by the examination 
may answer the fe mceeices : ac f beings of which the true nature and 
. d that consequently its conclusions ‘are more or 
“i ered ro enor i po long since conclusively answered in a letter of 
Prof. Heer to Sir Charles Lyell. 
