146 PALEOZOIC PALEONTOLOGY. 
its characters cannot be distinguished, but it is known that this 
valve also bears an internal, elevated platform somewhat similar to 
that of the brachial valve. The surface characters of the species 
cannot be recognized upon the New Jersey specimen. 
SCHIZOCRANIA FILOSA (Hall). 
Plate IX., Figs. 3—4. 
1875. Schizocrania filosa Hall and Whitfield, Pal. Ohio, vol. II., p. 
73, pl. 1, figs. 12-15. 
Description.—Shell orbicular or subovate, the beak of the free or 
brachial valve projecting slightly beyond the limits of the circle, giving 
a somewhat greater diameter along the median line than in a trans- 
verse direction. Pedicle or attached valve discoid, very thin, deeply 
and broadly notched on the posterior side; the notch occupying nearly 
one-quarter of the circumference of the valve on the outer margin 
and extending nearly to the centre of the valve, its border thickened, 
especially at the base, which is rounded, with the centre marked by 
a shghtly-projecting point, marked by strong, irregular, concentric 
undulations parallel to the margin, but interrupted by the border of 
the notch. Brachial or free valve moderately convex, most prominent 
near the centre, its surface marked by fine, even, thread-like, radiating 
strie, which increase both by bifurcation and intercalation, and be- 
come stronger toward the border of the shell. 
Remarks.—The specimens of this species found in the Trenton lime- 
stone of New Jersey compare favorably with specimens of similar age 
from New York, but they do not grow so large as is usually the case 
with specimens from the Cincinnatian beds of the Ohio valley. The 
pedicle or attached valve has not been observed among the New Jersey 
specimens, the description of this portion of the shell being taken 
from Ohio specimens. 
