DEVONIAN FAUNAS. 361 
little in front of the middle; margin convexly rounded from the an- 
terior extremity of the hinge-line to about the middle of the anterior 
side of the shell, where it is conspicuously sinuate; from this sinus 
it is again convexly rounded ventrally and posteriorly to the angular 
posterior extremity of the hinge-line. The body of the valve is 
moderately convex, the greatest elevation being above the middle. 
Anteriorly a convex wing is separated from the body of the shell by a 
rather narrow and abruptly-depressed, rounded sinus, which extends 
from a point just in front of the beak to the sinuosity of the anterior 
margin, the greatest elevation of this wing being about one-half that 
of the body of the shell. Surface of the entire valve marked by fine, 
flattened, radiating coste and by conspicuous, concentric lines of 
growth. Right valve unknown. 
The dimensions of an imperfect specimen are: height, 39 mm.; 
width, about 39 mm.; convexity, 10 mm. 
Remarks.—But a single imperfect specimen of the left valve of this 
species has been observed. It is in the condition of an internal cast, 
upon which the radiating surface markings are less sharply defined 
than upon the actual surface of the shell. It agrees essentially, so 
far as it is preserved, with Hall’s original illustration of the species, 
and there can be no doubt as to its correct identification. 
GASTROPODA. 
PLATYOSTOMA VENTRICOSA Con. 
Plate) XGUEXe, Kies, Fld: 
1859. Platyostoma ventricosa Hall, Pal. N. Y., vol. IIL., p. 469, pl. 
112, figs. 1-10, pl. 113, figs. 7-8, pl. 115, fig. 8; also, 
p. 475, pl. 118, figs. 3-9. 
Description.—Shell variable, more or less subglobular in form, 
consisting of three or four rather rapidly-expanding volutions, which 
may be contiguous throughout or the outer one may be more or less 
free. Spire not at all or but moderately elevated above the outer 
volution. Aperture slightly oblique, subcircular, suboval or sub- 
elliptical in outline. Surface marked by fine, more or less irregular, 
transverse lines of growth, which are sometimes more or less fascicu- 
late at intervals. 
