SILURIAN FAUNAS. 2AS 
line. Whole surface of the valve covered with narrow, angular, raised 
strie, with interspaces two or three times the width of the ridges, 
and by similar concentric strie. Right valve not seen. 
The dimensions of a nearly-perfect left valve are: length, 10.5 mm., 
and height, 9.5 mm. 
Remarks.—This little shell is rare in the Decker Ferry fauna, but 
it seems to agree in all essential characters with P. emacerata Con. 
of the Niagaran fauna. The typical representatives of the species 
occur in the Rochester shale of Western New York and are larger 
than the New Jersey shell. Because of their mode of preservation, 
they are also usually crushed so as to appear less convex. In form, 
proportions and markings, however, the shells from the two localities 
are essentially identical. 
PTERINEA? sp. undet. 
Description.—A single imperfect specimen of an oblique, winged 
shell, marked by alternately larger and smaller, radiating ribs, is, 
perhaps, a member of the genus Pterinea. So far as can be judged, 
its dimensions are: length, about 20 mm., and height, about 18 mm. 
PTERONITES ? SUBPLANA (Hall). 
Tate NONGIOES RS o9 aie 
1852. Avitcula subplana Hall, Pal. N. Y., vol. I1., p. 283, pl. 59, 
fig. 3 a—c. 
Description. — Left valve depressed-convex, winged posteriorly, 
subovate in outline, apart from the posterior extension of the hinge- 
line; beak nearly terminal, hinge-line equaling the greatest length of 
the shell. From the anterior extremity of the hinge-line the margin 
curves regularly to the postero-ventral angle, the curvature becoming 
more gentle posteriorly; it then curves rather abruptly into the 
posterior margin, which is sinyate and meets the posterior extremity 
of the hinge-line at an acute angle. The entire surface of the shell 
is marked by rather fine, somewhat irregular, concentric lines of 
growth, with no indications of radiate markings. 
