330 
Aug. F. Foerste 
of this valve along the upper part of its umbonal ridge is perfectly 
normal for the species, as typified by numerous specimens, entirely 
uncompressed, found at the type horizon. 
In more recent years I have found specimens of Byssonychia 
richmondensis as far off as Manitoulin island, and there also have 
noted the evidence of moderate antero-lateral compression resulting 
in a more elongate appearance of the shell, and in a greater angu- 
larity along the umbonal ridge. 
If Byssonychia richmondensis of Ulrich represents a form dis- 
tinct from those which I have identified as equivalent to his species, 
then I have never seen his species. 
In Byssonychia robusta there are about 30 to 33 radiating plica- 
tions posterior to the sharpest part of the umbonal ridge, and 8 or 
9 additional ones between this part of the umbonal ridge and the 
base of the byssal opening. The species occurs both in the Saluda 
and in the Whitewater members of the Richmond, the former being 
regarded as chiefly a southern more arenaceous, less fossiliferous 
phase of the greater part of the Whitewater and of a small part of 
the Elkhorn member of the Richmond group, as exposed farther 
north in Indiana. 
37. Cymatonota cylindrica, Miller and Faber 
{Plate VI, Figs. 7 A, B) 
1891. Orthodesma cylindricum Miller and Faber, Jour. Cincinnati Soc. Nat. Hist., 
17, p. 22, Plate 1, Figs. 1-1 
The types of Orthodesma cylindricum are numbered 8801 in 
the Faber collection at Chicago University. They are described 
as coming from above the middle of the Cincinnatian series of rocks 
in Warren county, Ohio, but are labelled as coming from Cincinnati, 
Ohio. Of the specimens figured by Miller and Faber, the one used 
for figure 1 is missing. The specimen used for figures 2 and 3 is 
fairly well preserved, and is illustrated in the present bulletin. 
The original of figure 4 is considerably distorted but shows the 
characteristic wrinkles along the hinge-line and the concentric striae 
of the general surface of the shell very well. The type evidently is 
identical specifically with Cymatonota typicalis described by Ulrich 
from theWaynesville member of the Richmond group atWaynesville, 
Ohio. Miller and Faber^s description was published in 1894, while 
Ulrich's description, was published, in volume 7 of the Geology of 
