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 



Figure syi 



San Pedro to Lower California. 



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 



Figure 37!^ 



West Coast of Central America. 



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 



