44 
MARINE SHELLS OF WEST COAST OF NORTH AMERICA 
Shell rather narrow, whitish or brownish, with 34-38 close, acute 
annulations, and subconcave interstices; septum subungulate, apex obtuse, 
not elevated. Length, .09 inch. (Dali.) 
Type in United States National Museum, No. 15719. Type locality, 
San Diego, California. 
Range. Monterey, California, to Lower California. Fossil: Pleis¬ 
tocene, San Pedro, San Diego, California. Pliocene, San Quentin Bay, 
Lower California. 
This is the most abundant West American Caecum. (Dali.) 
Paul Bartsch is working on the family Caecidac and the following is 
his classification: 
Caecum dalli Bartsch, 1920 
Type in United States National Museum, No. 340724. Type locality, 
San Diego, California. 
Range. San Diego, California, to Lower California. 
Caecum grippi Bartsch, 1920 
Height, 2.5 ; diameter, 0.7 mm. (Bartsch.) 
Type in United States National Museum, No. 206961. Type locality, 
San Diego, California. 
Range. Known only from type locality. 
Caecum licalum Bartsch, 1920 
Height, 2.2; diameter, 0.5 mm. (Bartsch.) 
Type in United States National Museum, No. 340725. Type locality, 
San Diego, California. 
Range. Monterey to San Diego, California. 
Caecum diegense Bartsch, 1920 
Height, 2.0; diameter, 0.4 mm. (Bartsch.) 
Type in United States National Museum, No. 340726. Type locality, 
San Diego, California. 
Range. Known only from type locality. 
Genus MICRANELLUM Bartsch, 1920 
Surface of the shell marked by closely spaced, slender, axial annula¬ 
tions; operculum thin, corneous, concave. (Bartsch.) 
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