384 PALEOZOIC PALEONTOLOGY. 
MOLLUSCA. 
PELECYPODA. 
ACTINOPTERIA sp. undet. 
A few fragmentary specimens of Pelecypod shells which evidently 
belong to the genus Actinopleria have been observed in the Monroe 
shales. None of them are complete enough for specific identification, 
but they resemble, in general, the New York Hamilton members of the 
genus. 
PALAEONEILO EMARGINATA (Con.). 
Plate LIII., Figs. 10-11. 
1885. Palwoneilo emarginata Hall, Pal. N. Y., vol. V., pt. L., p. 338, 
pl. 50, figs. 1-11. 
Description.—‘Shell of medium size or larger, subelliptical; length 
usually more than twice the height; basal margin gently curving or 
nearly straight from the post-inferior angle to the anterior end, where 
it is more abruptly rounded; posterior margin deeply sinuate. 
Cardinal line gently arcuate. Anterior end regularly and somewhat 
abruptly rounded. Valves regularly convex in the lower anterior 
half, becoming gibbous above. Beaks a little less than the anterior 
third from the end, and, except in the shorter forms, moderately 
prominent. Umbonal slope marked by a strong elevation or ridge, 
with a depression above it, which produces a marked emargination. 
The post-cardinal extremity, above this, is produced into a linguiform 
extension, which is sometimes angular, but usually abruptly rounded 
at the termination. Surface marked by strong, elevated, distant, 
lamellose, concentric ridges, extending the entire length of the shell, 
between which are very fine concentric strie. The intermediate strie 
become obscure or obsolete, according to the degree of weathering and 
nature of the matrix. 
“Five specimens measure respectively 22, 24, 26, 27, 28 and 40 mm. 
in length, and 12, 13.5, 16, 12 and 16 mm. in height.”—Hail. 
