386 
PALAEONTOLOGY OF ILLINOIS. 
The figure and description given of this species in the 2d vol. of this Report, 
p. 431, pi. xxxvii, fig. 1, arc imperfect, being made from the only specimen 
found at the time. Better specimens now on hand show that this fern evi¬ 
dently belongs to the genus Neuropteris , not only by its nervation, but by its 
ramification and the position of the leaves on the rachis. The species nearest 
to this is Neuropteris crenulata, Brgt., easily distinguished by its elongated nar¬ 
rower leaves, with crenulate rather than toothed borders, and the thickness of 
its veinlets. Our fig. 5 represents a specimen whose upper leaflets, scarcely 
dentate, have the surface wrinkled around, and marked by points of irregular 
size, placed without order, which resemble traces of fructification, the epider¬ 
mis appearing as if it had been perforated by glomerules of spores placed under 
it. This peculiar appearance may result from the process of maceration. It 
is too obscurely marked to merit more than a passing ndention. 
i ,b.£> 
Neuropteris rarineryis, Bunb. 
PI. viii, fig. 1 to 6. 
The specimens figured 1 to 4 on this plate, from the concretions of Mazon 
creek, bear round leaflets, apparently attached on both sides of a secondary 
rachis, as are generally the pinnules of a Neuroptei-is. According to this ap¬ 
pearance we should have not only to consider these leaves as representing a 
new species, but also to accept the genus Nephroptei'is or Cyclopteris for their 
classification. But I think that the parts represented in fig. 1 and 2, are not 
fragments of a secondary pinna with alternate pinnules attached to it, but only 
parts of primary pinnae with the basilar leaflets of the secondary pinnae at¬ 
tached to them, in the same way as such leaflets are attached along the rachis 
in fig. 6, which represents a fragment of pinna of Neuropteris rarinervis. 
This remarkable specimen is also from Mazon creek. As is easily seen, it 
shows a primary rachis with the base of its divisions marked by the remains 
of the secondary branches and the two basilar leaflets on each side of them. If 
this^branch^were longer, we should see these basilar leaflets more and more en¬ 
larged, becoming round farther down, and then showing the same forms as we 
see on fig. 1 and 2. In vol. 2, p. 429, in a foot-note of this Report, mention 
is made of a specimen from Newport, R. I., which bears on the same part of a 
frond two round cyclopteroidal leaflets attached at the axil of secondary pin¬ 
nae, while the same pinnae bear true neuropteroidal oblong pinnules, with a 
medial nerve. As this specimen elucidates the position of the two kinds of 
leaflets, and as it is the only one found as yet elucidating this peculiar differ¬ 
ence, I have figured it fig. 5, as affording the most conclusive representation of 
the unity of both the genera Neuropteris and Nephropteris. This figure, I 
