526 PALEOZOIC PALEONTOLOGY. 
CHONOSTROPHIA JERVENSIS Schuchert. 
Plate XLII., Figs. 1-2. 
1901. Chonostrophia jervensis Schuchert, Am. Geol., vol. XX VIL, p- 
250, figs. c—d. 
Description.—Shell subsemi-circular or subsemi-elliptical in out- 
line, hinge-line straight, usually equaling the greatest width of the 
shell. Cardinal extremities usually nearly rectangular, the lateral 
margins subparallel for a short distance, then curving into the 
broadly-rounded anterior margin. Pedicle valve slightly concave, 
cardinal margin straight, bearing on each side of the beak three or 
four spines directed obliquely outward, of which the outer ones are 
the larger, the others becoming regularly reduced in size; cardinal 
area flat, narrow. Brachial valve depressed-convex, flattened toward 
the cardinal extremities. Surface of both valves marked by fine, sub- 
equal, subangular, often somewhat wavy, radiating coste, which in- 
crease by intercalation, about four occupying the space of 1 mm. at 
the margin. These radiating markings are crossed by much finer 
concentric markings. 
The dimensions of an average specimen are: length, 9.5 mm.; 
width, 15 mm. 
Remarks.—This species is exceedingly abundant in the Dalmanites 
dentatus fauna, some layers or lenticular masses being constituted 
very largely of these shells. It is easily distinguishable from the com- 
mon Oriskany representative of the genus by its smaller size, its 
flatness and its fine and often somewhat wavy, radiating markings. 
DALMANELLA SUBCARINATA (Hall). 
Plate XLII., Figs. 3-4. 
See, also, p. 306. 
1859. Orthis subcarinata Hall, Pal. N. Y., vol. III., p. 169, pl. 12, 
s 
figs 7-21. 
Description—Shell subcireular or transversely subelliptical in 
outline, hinge-line shorter than the greatest width; cardinal ex- 
tremities rounded. Pedicle valve convex, subcarinate along the 
