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CAECIDAE 147
3.0 mm. in length by i.o mm. in diameter, opaque-white, with 20 to 30
strong, axial rings, the last 3 or 4 being quite large.
Caecum cayosense Rehder Key Caecum
rings.
Bonefish Key, Lower Florida Keys.
Shell similar to C. floridanuTn, but with about 14 very large, sharp axial
Caecum californicum Dall California Caecum
Monterey to Lower California.
Figure 37g.
2.0 to 3.0 mm. in length. With 30 to 40 moderately developed, evenly
spaced, rounded or squarish axial rings. Lip of aperture slightly thickened.
Color a glossy, olive-brown.
Caecum dalli Bartsch Dall's Caecum
San Diego to Lower California.
Figure ^jh
About 3 mm. in length, usually with 18 to 24 moderately developed,
evenly spaced, rounded or squarish, axial rings. Lip of aperture usually heavily
developed in adults. Color tan. The number of raised rings varies from
specimen to specimen, often in the same locality, and diligent search will
usually bring to light any number desired. Extremes have been unwisely
named (15 rings—C. grippi Bartsch; 17 to 19 rings—C. licalum Bartsch; and
19 to 22 rings—C. diegense Bartsch). Figure 37h is the holotype.
Subgenus iMicraneUum Bartsch 1920
Shells 3 to 7 mm. in length, opaque, with numerous, fine, closely packed,
axial rings. About 8 Eastern Pacific and perhaps half a dozen Western At-
lantic species in this subgenus.
Caecum pulcbelhnn Stimpson Beautiful Little Caecum
Cape Cod south to North Carolina.
Figure 370!
About 2 mm. in length, translucent-tan and glistening when alive;
chalky-white when dead; with about 25 to 30 fine, closely set axial rings.
Apex with a dome-shaped plug.
Caecum crebrictnctum Carpenter Many-named Caecum
Figure 37m
Monterey to Lower California.