OF DENISON UNIVERSITY. 
77 
to include our specimens from Ohio, but the average width of the Illi- 
nois is less than that of Ohio forms, and in general the size of speci- 
mens seems more variable at the former locality. Later in the Appen- 
dix to the Report of Surv. W. of looth Meridian, PL IV, Fig. 2, White 
figured one of the type specimens. This specimen falls below the 
minimum width given in the original description, being only 2.5 mm. 
wide, and is figured with scattered cells, irregularly undulating edges 
and without crescentic nonporiferous portions regularly occupying the 
incurved portions of the sides. However, since Fig. 2, e, on the 
same plate, representing a specimen from Cebolla Creek, likewise 
omits the crescentic non-poriferous characters of the margin, readily 
seen in the original specimens, it is to be expected that in a small speci- 
men this feature would be entirely overlooked. At any rate the small- 
est specimen we have from Danville, which is 3 mm. wide, shows the 
crescentic non-poriferous characters, the arrangement of cells noted in 
the Ohio specimens, and a regularly undulating margin, all the charac- 
ters being readily noted when attention has been once called to the 
same. 
Again, specimens from Chester, Illinois, of larger size, but of the 
same average width as Ohio specimens, show no variations from the 
latter in any particular. The same is true of the specimens just re- 
ferred to from Cebolla Creek, New Mexico, Nos. 4480, 9447, and 
9472 of the National Museum collections. In his Pal. Papers, No! 
XI, White describes specimens from the middle Carboniferous series 
of Yampa Plateau, N. W. Colorado, which are only 2 to 2.5 mm. 
wide. We found in them the same crescentic nonporiferous spaces 
as noted above in specimens from other localities. Finally, Ulrich 
described a form from Tateville and Grayson Springs, Kentucky. It 
is in every respect similar to the Ohio forms. He states: “This species 
is readily distinguished from all other species of the genus known to 
me by its wavy or serrated margins.” The three-sided character of 
Meek’s specimen was unknown ; White in his original description 
failed to mention the indentations of the margin, in his second descrip- 
tion they are stated to be merely a little irregular, but in his third 
description the scalloped character so readily noticed in larger speci- 
mens is distinctly stated and in one example figured. 
The general features of the species therefore consist in regularly 
scalloped margins ; the serrations are not rounded typically, but are 
more or less accurately truncated, sometimes even slightly concave, 
