GASTEROPODA OF THE LOWER GREEN MAKLS. 125 
be perfectly smooth on the top, as in Dr. Morton’s specimens. I have, 
however, given it a distinct specific reference and place in the volume, 
that, in case other specimens should be found, it may retain its individu- 
ality as a species. 
Formation and locality: In coarse ferruginous sand of the Lower Marls, 
at Mullica Hill, New Jersey. Collection Acad. Nat. Sei., Phila. 
GYRODES INFRACARINATA. 
Plate xv, Figs. 13-16. 
Natica infracarinata Gabb: Proc. Acad. Nat. Sci., Phila., 1861, p. 319, 
Gyrodes infracarinata (Gabb) Meek: Geol., N. J., Newark, 1868, p. 729. 
Shell, as shown by internal casts, large, depressed globular above and 
truncate below by the broad umbilical area shortening the depth of the 
shell; spire consisting of about four volutions, the last one of which forms 
fully two-thirds of the bulk of the entire shell; volutions oblique, largest 
below the middle, slightly flattened on the top adjacent to the suture, and 
very strongly angular on the base bordering the very wide open umbilicus, 
in which the volutions are exposed nearly to the apex; aperture large, 
ovate, widest below the middle and truncate at the upper angle by the flat- 
tening of the volution adjacent to the suture; columellar lip apparently 
quite thin, and marked by a single spiral thread-like ridge on its inner sur- 
face; outer lip sharp and thin and very strongly receding below, as seen in 
a profile view; surface of the cast usually smooth, but sometimes showing 
evidences of transverse striz of growth. 
The New Jersey specimens of this species are all internal casts, con- 
sequently the surface features are unknown. The casts indicate a strong 
robust species, with rapidly increasing volutions, which are short in com- 
parison to their lateral dimensions. The suture is very strongly marked, 
showing considerable thickening of the shell at the junction of the volu- 
tions. The features of the umbilicus are taken from specimens where the 
filling of this part has been taken out of the cast and preserves the surface 
markings, thereby giving the features in a perfectly reliable manner. The 
examples seen from New Jersey are not as large as those of G. abyssinus 
from the southern localities, but they are found having a diameter of nearly 
