/ 
334 Aug. F. Foerste 
Clarksville division are seen farther westward, along the same 
stream. From this it is assumed that the type was found in the 
upper part of the Waynesville. Three figures of the type are given 
in this Bulletin. 
There is no doubt of this type being merely the young of some 
species of Pholadomorpha, presumably Pholadomorpha pholadiformis. 
The figure accompanying the original description is slightly enlarged 
in the effort to represent the specimen as entire, and the prominence 
of the beak and of the umbonal ridge is greatly exaggerated. The 
basal margin is less convex than in this figure, especially posteriorly. 
The concentric wrinkles are strongly defined in case of the right 
valve, less strongly in case of the left valve. Along the cardinal 
margin these concentric wrinkles form angles of about 40 degrees 
with this margin; here they are fairly well defined if held transversely 
to the light. The chief difficulty in recognizing those parts of the 
concentric wrinkles which border on the cardinal margin is the 
presence of the transverse plications which make their appearance 
within 8 millimeters of the beak, and become more prominent pos- 
teriorly. On this account, only those concentric wrinkles which 
are near the beak are recognized readily on the postumbonal slopes. 
The transverse plications on the slope beneath the umbonal ridge 
are low and broad, but distinctly defined. 
There is no reason for believing that Sedgwickia divaricata 
represents a distinct species. It is merely a specimen of Phola- 
domorpha pholadiformis in which both the concentric wrinkles 
and the transverse plications were strongly defined even at an early 
stage of growth. This suggests that at mature age this type would 
have been characterized by strongly marked transverse plications 
even along the postumbonal slopes, as in the specimen figured as 
Pholadomorpha divaricata from the Richmond of the Riviere des 
Hurons, in the province of Quebec, in this Bulletin, volume 17, 
on plate 2. It is not certain, however, that the type of Sedgwickia 
divaricata would have developed into a form with as strongly di- 
vergent cardinal and basal margins as the latter specimen. 
42. Pholadomorpha capax, Miller 
{Plate V, Figs. l^A, B) 
1889. Modiolopsis capax Miller, N. A. Geol. Pal., pp. jli.89, Ii.90, Fig. 851 
The type of Modiolopsis capax, figured in this Bulletin, forms 
No. 8802 in the Faber collection at Chicago University, and retains 
