Vermetidae and Caecidae 137 



becoming increasingly more distant and irregular. Longitudinal sculp- 

 ture of one strong keel continuous with carina of juvenile whorls; 

 on one side of this keeled rib is a series of small ribs separated by 

 finely ribbed interspaces, threadlike ribbing over remainder of 

 surface; wrinkled annular growth lines. Aperture round; sharp ob- 

 lique margm; diameter about six millimeters. Small, concave, cor- 

 neous operculum. 



Vermicularia farg'oP*'^ Olsson {V. spirata Philippi) PI. 26, fig. 184 



Color brown, paler toward aperture. Apex of juvenile shell 

 acute, nucleus glassy; about six regular whorls preceding the long 

 loosely coiled portion of shell. Sculpture of longitudinal ribs which 

 form definite keels; smaller parallel ribs and fine interspatial 

 striations; rough, annular growth lines. Aperture round, diameter 

 eight to twelve millimeters. Operculum corneous, circular, entirely 

 closes aperture. 



V. fargoi IS eaten by Fasciolaria hxintena; Trivia pediculus has 

 been seen by Perry to devour large numbers of the veligers of Venni- 

 ctdaria. 



Family CAECIDAE 



This is a group of minute mollusks generally distributed through 

 warm and temperate seas at moderate depths. The shells are not 

 likely to be found unless carefully looked for in sifted sand or ac- 

 cumulations of fine detritus on the beaches between tide levels and 

 the sand which may be shaken from sponges. 



The embryonic shell is a spiral of two or three whorls, succeed- 

 ing development is into a horn-shaped tube — the bovi-cornu stage. 

 These juvenile phases of the shell are successfully truncated as 

 further growth proceeds; the shell when adult is small, tubular, 

 arcuate, with a circular aperture and an externally convex septum 

 which closes the apical end. 



Genus CAECUM Fleming, 1813 

 Caecnm246 floridanum Stimpson PI. 26, fig. 185 



Length, 2; diam., 6 mm. Shell white, arched; from 20 to 30 



-*^ Named for William Fargo; Lat, spira, a coil. 

 ~*^ Lat., caecus, blind. 



