238 
Kirtley F. Mather 
every respect typical individuals of this form which higher 
in the Pennsylvanian series becomes much more abundant. 
Horizon and locality. Hale formation: East Mountain, Fay- 
etteville, Arkansas (Station 139). Brentwood limestone: Kess- 
ler Mountain, Arkansas (Station 147), Morrow formation: near 
Ft, Gibson, Oklahoma (Station 301), 
STROPHOSTYLID^ 
Genus STROPHOSTYLUS Hall 
Strophostylus subovatus (Worthen) ? 
Plate XV, figures 28, 28a. 
1873. Naticopsis subovatus. Worthen, GeoL Surv. 111., vol. 5, p. 595, pi. 
28, fig. 9. 
Upper Coal Measures: LaSalle, Illinois. 
1898, Strophostylus subovatus. Weller, Bull. U. S. Geol. Surv., No. 153, 
p. 615. 
1903. Strophostylus subovatus ?. Girty, Prof. Paper, U. S, Geol. Surv,, 
No. 16, p. 463, pi. 10, figs. 3=3a. 
Middle portion of Hermosa formation: San Juan region, Colorado. 
Only one specimen of this form has come to hand. It is 
much smaller than the typical material and the shell from the 
Hermosa formation which Girty has referred with a query to 
this species. With the latter, however, it appears to agree 
closely in conformation and, although little more than half as 
large, a reference of the two to the same species seems alto- 
gether justifiable. It is possible that this early Pennsylvanian 
form should be separated specifically, or at least varietally, 
from the Upper Coal Measures type. 
Horizon and locality. Hale formation: East Mountain, Fay- 
etteville, Arkansas (Station 136). 
Genus PLATYCERAS Conrad 
Platyceras parvum (Swallow) 
Plate XV, figure 28. 
1858. Capulus parvus. Swallow, Trans. St. Louis Acad. Sci., vol. 1, p, 
205. 
Coal Measures: Valley of the Verdegris, Kansas. 
1872. 
pi. 4, figs. 15a-b, 
Upper Coal Measures: Three-fourths of a mile west of Nebraska 
City Landing, Nebraska. 
Middle Coal Measures: Illinois. 
