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 



Figure 37c 



North Carolina to southern Florida. 



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 



Figure 37f 



Missouri Key, Florida Lower Keys. 



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 



Figure 37I 



San Pedro to Lower California. 



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 



Figure 37) 



Alaska to Lower California. 



2.2 to 3.5 mm. in length. Smooth, except for fine, circular scratches. 

 Shell elongate, round in cross-section. Aperture moderately oblique; apical 



