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148 American Seashells
6.0 mm, in length. Color pinkish brown to chalky-white with occa-
sional darker brown mottlings. With about loo fine, squarish, closely set
axial rings. Plug with a rather long, oblique spur. Spur sometimes eroded
down to a small sharp pimple (form oregonense Bartsch). Irregularities oc-
cur in the expansion of the tube; sometimes there is a more rapid expansion
toward the anterior end (forms named as species: C. pedroeiise Bartsch and
C. barkleyense Bartsch). C. catalinense Bartsch is probably this species, since
many of the paratypes do not have the anterior end supposedly "bulbously
expanded," and many specimens have about loo axial rings, and not 75 as
claimed. C. rosaniim Bartsch appears to be a very long specimen (7 mm.)
with sharply defined rings. Common.
Subgenus Elephantanellwn Bartsch
3 to 5 mm. in length, white, with axial rings and longitudinal ribs. One
species in southern California and 3 or 4 in the Western Atlantic. They
resemble minute scaphopods, but are distinguished from them by the apical
plug and small size of the shell.
Caecum cooperi S. Smith Cooper's Atlantic Caecum
Figure 37b
South of Cape Cod to northern Florida.
4 to 5 mm. in length, slender, glossy, opaque-white; with about 15
strong, longitudinal ribs. Axial, raised rings are prominent near the aperture
and sometimes give the shell a cancellate appearance at the anterior end.
Apical plug with a fairly long, pointed prong. Common.
Caecum carpenteri Bartsch Carpenter's Caecum
San Pedro to Lower California.
Figure syi
3.5 to 4.8 mm. in length. First half to first % of shell smooth, but at
the apertural end developing about a dozen small, sharply defined axial rings.
Longitudinal sculpture microscopic or absent. Color translucent-white to
gray. This species is doubtfully placed in this subgenus.
Caecum heptagonum Carpenter Heptagonal Caecum
West Coast of Central America.
Figure 37!^
2.0 to 2.5 mm. in length. Opaque-white. 7-sided in cross-section. The
7 longitudinal ribs arc strong, raised, and the spaces between them are flat or
slightly concave. There are about 30 deeply cut circular lines around the