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CAECIDAE 149
shell, cutting across the ribs. Lip of aperture with one or two swollen axial
rings.
Subgenus Levia de Folin 1875
Rather thick, glossy, slightly curved shells; aperture minutely con-
stricted; sculpture absent except for microscopic growth lines. The shells are
larger, heavier and not as bulbous as those in the subgenus Fartulum.
Caecum caroliniammj Dall Carolina Caecum
North Carolina to southern Florida.
Figure 37c
About 4.5 mm. in length, glossy, cream-white. Smooth except for micro-
scopic growth lines. Apical plug sunk in at the posterior end of the shell and
with a sharp, horn-like projection. Aperture minutely constricted.
Subgenus Fartidiini Carpenter 1857
Shells very small, about 2 mm. in length, fragile, smooth, except for
microscopic growth lines; not swollen in the middle; and with a noncon-
stricted aperture facing to one side (oblique).
Caecum nebulosuin Rehder Mottled Caecum
Missouri Key, Florida Lower Keys.
Figure 37f
1.5 to 2.0 mm. in length, fragile, translucent-tan with opaque-white mot-
tlings. Not swollen in the center. Aperture oblique. Apex with a lopsided
plug which has a single, weak spur. Found under flat rocks imbedded in
tough, sticky marl.
Caecum orcutti Dall Orcutt's Caecum
San Pedro to Lower California.
Figure 37I
2.0 to 2.5 mm. in length. Smooth, except for fine, circular scratches.
Shell stubby, slightly compressed laterally; aperture oblique; apical plug
dome-shaped. Color translucent-tan to yellow-brown. Moderately common.
Caecum occidentale Bartsch Western Caecum
Alaska to Lower California.
Figure 37)
2.2 to 3.5 mm. in length. Smooth, except for fine, circular scratches.
Shell elongate, round in cross-section. Aperture moderately oblique; apical