Foerste.] 
328 
[May 1, 
Ptilodictya expansa, emarcescens var. nov. 
(PLATE VI, FIG. 30.) 
A single specimen was collected at Eaton, Ohio, by Mr. J. M. 
Nickles, which is so readily distinguished from all other forms 
known, as to warrant its description. It belongs to the type of 
Ptilodictyce already known from the Clinton of Ohio from Ptilodictya 
expansa , Hall and Whitfield. The frond is composed of two layers 
of cells united by their epithecal membranes. The sides of the 
frond are parallel, the fronds are very much flattened, very mod- 
erately convex from side to side, about 3.G mm. broad. There is 
a central band composed of about five rows of cells, 1 mm. broad, 
the cells being shorter longitudinally than the lateral cells, about 
eight cells occupying a length of 2 mm. These cells have a ten- 
dency of being arranged more directly across the fronds than the 
lateral cells ; the central band is not well differentiated from the 
lateral rows of cells, sometimes encroaching upon the latter, some- 
times the reverse. 
On the right side of this band in the frond here described there 
are eight rows of cells ; on the left side, also eight rows. These 
rows are always readily distinguished from the fact that the cells 
are longer, six cells occupying a length of 2 mm. ; they are also 
narrower, six cells occurring laterally in 1 mm. They are also dis- 
tinguished from the fact that these cells are arranged in very per- 
fect rows diagonally, the diagonal rows forming an angle of about 
15° with aline drawn transversely across the frond. This spec- 
imen is distinguished from Ptilodictya expansa solely by its small 
size, the young specimen of that species which have come fre- 
quently under our observation always having greatly exceeded the 
Eaton form in size. 
Ptilodictya farctus, sp. nov. 
(plate VI, FIG. 31.) 
Another form of Ptilodictya found at Eaton, Ohio, by Mr. J. M. 
Nickles is also represented by a single and very unique specimen. 
It is about 9 mm. long. The average width is 2 mm. and the av- 
erage thickness, 1.4 mm. Indeed the frond looks like an almost 
cylindrical stem a little flattened transversely. A low-power lens 
will reveal on either side of this stem a sharp line which marks the 
position of the epithecal membrane, and is ready evidence of its be- 
