166 MOLLUSCA. 
finely grooved with somewhat oblique, long, smutty folds, edentulous; 
left lip concave, shining, bluish-black, with a few very fine granules at 
the middle; middle of the edge concave, and with three very minute 
teeth ; fauces bright yellow. 
Axis one-half of an inch; diameter five-eighths of an inch. 
This unusually-shaped Nerite looks like a Stomatella, with the 
whorls rounded in every direction, when viewed at the back. Its 
general form is somewhat like N. szgnata. It is remarkable for its 
nearly circular, cup-shaped aperture, its shining black, finely granu- 
lated concave pillar, and its gray, minutely mosaic surface, produced 
by the white lines crossing its ridges. 
Nerita crassa (Gould). 
Testa soldissima, sub-globosa, longitrorsum striata, spiraliter sulcato- 
costata (costis ad triginta rotundatis), fusco-cinerea, flammulis crebris 
angulatis obliquis variegata: spira prominula, ad apicem lutea ; an- 
fractibus quatuor rotundatis ; sutura impressa : apertura parva, semt- 
circularis ; labro crassissimo, anciso, crenulato, intus sulcato, posticé 
unidentato ; lahio angusto, octo-plicato, plicis anticis bisectis ; colu- 
mella bidentata, dente antico minimo. 
SHELL globose, very solid, of a reddish ashy tint, varied with inter- 
rupted black lines on the ribs, so arranged as to form numerous, ob- 
lique, zigzag, longitudinal stripes. Spire elevated, bright yellow at 
tip; whorls four, on the last of which are about thirty cord-like ribs, 
crossed by coarse lines of increment, making the tip a little granular. 
Aperture rather more than half a circle; lip very thick, cut square 
across and not sharpened to an edge, having about twelve sulci within, 
and a single large tooth posteriorly; inner lip nearly plane, rather nar- 
row, with about eight folds, the four anterior of which are bisected by 
a transverse groove ; teeth of the columella two, of which the anterior 
is smallest. 
Diameter one inch; axis three-fourths of an inch. 
I have some hesitation in designating this shell as a new species, 
