78 
Surface of both valves ornamented by concentric growth lines and 
by low, rounded, concentric ridges varying somewhat in width; medially 
near the base these ridges are from 1 mm. to 1*75 mm. wide. The ridges 
cover the entire shell, including the umbo, but are very weak upon the 
flattened posterior cardinal slope. There are faint indications of radial 
lines upon the anterior slope. 
Remarks. This species is founded upon a single, partly exfoliated 
Bhell. Generieally it somewhat resembles Sanguindites, but the anterior 
adductor muscle scar shows no indication of the buttress characteristic of this 
genus; if the buttress were present there should be some indication of it 
upon the exfoliated left valve. Specifically it approaches rather closely 
to A. cuyahoga Herrick 1 from the Waverly of Ohio, but iB more elongate, 
narrower posteriorly, less extended antero-basally, and has much weaker 
concentric ridges upon the postero-cardinal slope. 
Locality and Horizon . In the Minnewanka region in the Mississippian 
of section 2-24 (R). 
Genus, Pleurophorus King 
Pleurophorus tropidophorus Meek 
1875. Pleurophorus tropidophorus Meek, Pal. Ohio, vol. 2, p. 338, PI. 19, 
figs. 10 a-b; Herrick, 1887, Bull. Sci. Lab. Denison Univ., vol. 2, 
p. 35, Pl. 4, fig. 15; Beede, 1900, Univ. Geol. Surv., Kansas, vol. 6, 
p. 162, Pl, 20, fig. 7; Mark, 1911, Bull. Sci. Lab. Denison Univ., 
vol. 16, p. 312, Pl. 10, fig. 11; Mather, 1915, Bull. Sci. Lab. Denison 
Univ., vol. 18, p. 230. 
Locality and Horizon. Pennsylvanian from Ohio to Arkansas. In 
the Minniwanka region in the Pennsylvanian of section 2-10 (R). 
cf. Pleurophorus mexicanus Girty 
1909. Pleurophorus mexicanus Girty, U.S. Geol. Surv., Bull. 389, p. 91, 
PL 10, fig. 1. 
Remarks. Our single specimen is an imperfect left valve. It appears 
to approach most closely to this species but clearly cannot be identified 
with it. It is similar to Girty' s species in its posterior outline, surface 
ornamentation, the low ridge paralleling the hinge-line, and in the evidence 
of a faint umbonal ridge; this ridge is, however, much fainter as is likewise 
the ridge which parallels the hinge-line, and the one or two parallel ridges 
between these in Girty' s species are completely lacking in ours. The 
anterior part, including the beak, is destroyed. Length about 65 mm., 
breadth about 20 mm. 
Locality and Horizon. In the Minnewanka region in the Permian 
of section 1-14 (R). 
i Geol. Surv., Ohio, vol. 7, Pl. 22, fig. 17. 
