314 PALEOZOIC PALEONTOLOGY. 
umbo prominent, beak incurved over the rather wide and sharply- 
defined, concave, cardinal area, much extended beyond that of the 
opposite valve; mesial sinus deep, rounded in the bottom, reaching 
to the beak, extended in front. Brachial valve nearly or quite as 
convex as the pedicle valve, most prominent on the rounded mesial 
fold near the anterior margin. Surface of both valves marked by six 
to eight abruptly and strongly-elevated, subangular plications on each 
side of the fold and sinus; covered, also, by strong, imbricating, con- 
centric lamelle, which are abruptly arched in passing over the plica- 
tions, giving to the entire surface an extremely rough appearance. 
The dimensions of an average-sized specimen are: length, 22 mm. ; 
width, 34 mm.; thickness, 15 mm. 
Remarks.—This species is common in the lower portion of the New 
Scotlond beds. The New Jersey specimens differ in no particular from 
those which occur so abundantly in the same formation in New York 
State. 
SPIRIFER CYCLOPTERUS Hall. 
Plate XXXVIIL., Figs. 1-6. 
1859. Spirifer cyclopterus Hall, Pal. N. Y., vol. III., p. 199, pl. 25, 
figs. 1 a—z. 
Description —Shell usually wider than long, varying from semi- 
circular to transversely subelliptical in outline; the hinge-line usually 
shorter than the greatest width, with the cardinal angles rounded, 
but sometimes the hinge-line is extended, with the cardinal angles 
angular. Pedicle valve: strongly convex, the umbo prominent, the 
beak elevated and more or less incurved over the small, ill-defined, 
coneave, cardinal area; mesial sinus of moderate depth, non-plicate, 
rounded in the bottom. Brachial valve with about the same convexity 
as the pedicle, mesial fold abruptly elevated, prominent. Surface of 
each valve marked by from five to seven rounded plications on each 
side of the fold and sinus, which are crossed by fine, more or less 
prominent, imbricating lamellae, which are ornamented with fine, ver- 
tical striz near their outer edges. 
