344 PALEOZOIC PALEONTOLOGY. 
been definitely recognized from the New York State line to below 
Hainesville. The external surface of the shells usually adheres to the 
matrix, so that they are badly exfolated, the interior surface being 
more commonly preserved than the exterior. The apical portion of 
the pedicle valve, including the pedicle opening, is usally destroyed, 
leaving an irregular, subcentral opening through that valve. 
PHOLIDOPS ARENARIA Hall. ? 
Plate XLYV., Fig. 6. 
1867. Pholidops arenaria Hall, Pal. N. Y., vol. IV., p. 413, pl. 3, 
fig. 3. 
Description.—Shell rather large, subcircular or slightly longi- 
tudinally subelliptical in outline. On the casts of the brachial valve 
the muscular impressions are situated on an abrupt, subcircular eleva- 
tion a little excentrically located toward the posterior margin, the 
elevation being somewhat more abrupt posteriorly. ‘The entire 
marginal border is flattened. The casts of the anterior adductor 
muscular impressions are excavated from the central elevation; they 
are subovate or subelliptical in outline, their axes diverging pos- 
teriorly, and are separated by a median ridge or elevation which is 
narrow in front but grows rapidly broader posteriorly. The external 
surface characters have not been observed. 
The dimensions of a nearly-complete cast of one valve are: length, 
% mm.; width, 7 mm. 
Remarks.—Only the casts of what is usually supposed to be the 
brachial valve of this species have been observed. The size of the 
species is above the average of members of the genus, and it may be 
distinguished by this character and by its more or less subcircular 
outline. The New Jersey specimens do not agree exactly with Hall’s 
original illustraton of the species, and there may be some question 
as to their correct identification. 
