230 
Kirtley F. Mather 
growing successively fainter anteriorly until over the extreme 
anterior portion of the valve radiating lines cannot be observed, 
ears and adjacent umbonal slopes smooth. 
Dimensions of the type specimen are : length, 13.5 mm. ; 
height, 11.0 mm.; convexity of valve, about 3.0 mm.; hinge- 
line, 5.6 mm. 
Remarks. This internal cast of a left valve from the Kessler 
limestone bears such close resemblance in shape to the shells 
which Hind has grouped under the name Palaeolima that it is 
provisionally placed in that genus. The species resembles most 
closely P. ohliquiradiata but is obviously distinct from it. 
Horizon and locality. Kessler limestone: East Mountain, 
Fayetteville, Arkansas (Station 209). 
PLEUROPHORID^ 
Genus PLEUROPHORUS King 
Pleurophorus tropidophorus Meek 
1875. Pleurophorus tropidophorus. Meek, Pal. Ohio, vol. 2, p. 338, pi. 19, 
figs. lOa-b. 
Coal Measures: Newark, Ohio. 
1887. Pleurophorus tropidophorus. Herrick, Bull. Sci. Lab. Den. Univ., 
vol. 2, p. 35, pi. 4, fig. 15. 
Coal Measures: Flint Ridge, Ohio. 
1900. Pleurophorus tropidophorus. Beede, Univ. Geol. Surv. Kans., vol. 6, 
p. 162, pi. 20, fig. 7. 
Upper Coal Measures: Kansas City, Missouri. 
1911. Pleurophorus tropidophorus. Mark, Bull. Sci. Lab. Den. Univ., vol. 
16, p. 312, pi. 10, fig. 11. 
Mercer limestone: Limestone Hollow, Flint Ridge, Ohio. 
This species is represented in the material at hand by a single 
specimen of a right valve from which the anterior third is miss- 
ing. The outline, umbonal ridges, and surface markings con- 
form so closely to Meek’s description and figures that the refer- 
ence to his species is made with considerable confidence. 
Horizon and locality. Hale formation: East Mountain, Fay- 
etteville, Arkansas (Station 136). 
