Bulletin - United States National Museum - Smithsonian Institution

114 BULLETIN 91, UNITED STATES NATIONAL MUSEUM.
and are crossed by numerous slender, quite regular, and regularly
spaced axial riblets, which extend up on the sides of the spiral cords,
but do not cross their summit. In addition to these axial riblets,
the grooves between the cords are marked with many very fine, in-
cised, spiral lines. Sutures moderately constricted. Periphery of
the last turn angulated, the angle being formed by the fourth spiral
cord. Base short, well rounded, marked by two spiral grooves, one
of which forms the boundary for the anterior keel between the
sutures, and is crossed by slender axial riblets like the spiral grooves
on the spire, while the other, which is less strong, limits the columella.
The space between these two grooves is crossed by numerous, fine,
spiral striatums and incremental lines. Aperture moderately large,
subquadrate, decidedly channeled anteriorly. Posterior angle very
obtuse; outer lip thick, rendered sinuous by the external spiral cords;
columella short, strongly curved, and slightly reflected over the rein-
forcing base; parietal wall glazed with a moderately strong callus.
There are eight specimens of this species in the United States National
Museum. Cat. No. 1S6802, collected at Port Alfred (Coll. No.
167). Two of these have served as cotypes, one having nuclear
characters and the other showing the adult structures. Our figure
is a composite one built upon these two specimens. The smaller of
these two specimens has ten postnuclear whorls, and measures:
Length, 8.5 mm.; diameter, 2.5 mm. The adult specimen, having
lost the nuclear and the early whorls, has 10 whorls remaining, which
measure: Length, 10 mm.; diameter, 3.1 mm.
SEILA AFRICANA, new species.
Plate 17, fig. 6.
Shell regularly elongate-conic, chestnut brown, a little lighter on
the early whorls. (Nuclear whorls decollated) . Postnuclear whorls
flattened, marked with strong flattened spiral keels, of which three
occur upon all the whorls between the sutures. The first of these
is a little anterior to the summit, leaving a somewhat concave shoulder
at the summit; the last is an equal distance above the suture; while
the second is midway between the two. These keels are separated
by deep, concave grooves which are a little wider than the keels.
In addition to these spiral keels, the whorls are marked by exceed-
ingly fine, closely-spaced, axial, raised threads, which cross the
deep grooves that separate the spiral keels, the sutures appearing
like the grooves on the whorl. On the last three whorls the summit
of the turns falls slightly anterior to the peripheral cord, which shows
partly in the suture. Periphery of the last whorl decidedly angulated,
marked by a cord a little less strong than those occurring upon
the spire. Base moderately long, well rounded, marked by two
spiral cords, of which the first is about as far anterior to the peripheral