54 THE NAUTILUS. 
irregularly pitted as in A. lattrei, and the microscopic spiral 
strize are more plainly defined. 
The embryonic whorls are dark-colored, almost black. 
Height 42, breadth 40; aperture, length 33, width 18 mm. 
Height 40, breadth 37.5; aperture, length 32, width 20 mm. 
Specimens of exactly this form were collected about twenty 
years ago at ‘‘ Rio Negro, Chama,”’ by S. L. Schumo, a mem- 
ber of the Philadelphia Academy of Natural Sciences. 
Four specimens were brought to the writer by an Indian; one 
(figured) is in the Academy coll., one in coll. of Mr. Bryant 
Walker, one in the Museum of the Illinois University, and the 
writer has the other. 
PACHYCHEILUS POTTSIANUS N. Sp. 
Shell pyramidal, solid, smooth, of a dingy olive color; whorls 
eight, hardly convex, a light shade below the suture, the last 
slightly and broadly depressed on the upper part, in front of 
the aperture the periphery is obtusely angular, the angle dimin- 
ishes with the ‘growth of the whorl until the last of the body 
whorl is broadly rounded. Suture shallow, distinct. . Aperture 
ovate, angular above, circular below, chocolate-colored within, 
parietal callus well defined and much thickened above, labium 
slightly thickened. Operculum ovate, nucleus depressed. 
When the mollusk is in its natural position the shell as viewed 
from above has the appearance of the penult whorl being 
humped and the under side of the shell is nearly always eroded 
as if it had been worn away in moving about. Four specimens 
measure: 
Length 44, width 17. Aperture, length 14, width 8 mm. 
Length 41, width 17. Aperture, length 14, width 8 mm. 
Length 40, width 16. Aperture, length 15, width 74 mm. 
Length 42, width 17. Aperture, length 14, width 84 mm. 
This species was taken from two rills on hillsides, in dense 
woods. Often there was only enough moisture to keep the 
shells damp, or they were under fallen leaves; with them where 
there was a half inch or more of water were P. pyramidalis, from 
which they differ in being smaller and without any sculpturing. 
They are wider than P. indiorum of the same length, and have 
