382 L. Lesquereuz on the Coal Formations of North America. 
in diameter, the scars are not quite one inch broad. Now the 
largest and most remarkable specimen of a Caulopteris that I 
have ever seen and a notice of which has ever been published 
(Caulopteris insignis Lsqx.), shows a piece of bark with a single 
but entire cicatrice of just three inches in diameter. Admitting 
that the proportion of the cicatrices to the stem is, in this species, 
the same as in the former ones, this must have belonged to a 
trunk of fern of less than one foot in diameter. This agrees well 
with the size of the trunks of Psaronius of Shade river, whose 
diameter is mostly between four and eight inches, rarely reach- 
ing one foot. 
The genus Megaphytum Art. should, according to Prof 
sears of fascicles of vessels, in the form of a horse-shoe; just 
like the Caulopteridec, but without a marked annulus. These 
Brongniart supposes. It is even evident, from the forms of 
the cicatrices, which are a little flattened at their base and more 
elevated at the upper part, that the fronds which were ong 
attached to them were ascendent and closely appresse a 
deeply and irregularly striated and furrowed as if it had me 
covered by rootlets, just like the surface of a Psaronius. The 
cicatrices of Megaphytum Wilburianum Lsqx., still more a : 
wi 
the genus Megaphytum as intermediate between the Ly 
and the ferns. 
Calamitaric. 
The species of this group of fossil plants have as ape : 
, with 
characters: the stems hollow, regularly striated, articulate 
articulations more or less distant, marked by a depressed or 
: cular ring, or by an elevated margin, bearing whorl: 
: ants: of the Coal Measures, which have been P. 
or less united at their base. ‘The five principal genera Of 
