no. 1823. MOLLUSKS OF THE OENUS CERITHIOPSIS— BARTXCH . 333 



dered sinuous by the external sculpture; columella very stout, twisted 

 revolute, and reflected; parietal wall glazed with a thin callus. 



The type and another specimen (Cat. No. 106505, U.S.N.M.) come 

 from Point Abreojos, Lower California. The type has seven post- 

 nuclear whorls and measures: Length 3.3 mm., diameter 1.2 mm. 

 Two additional specimens (Cat. No. 195181, U.S.N.M.) come from 

 San Pedro Bay, California. 



CERITHIOPSIS (CERITHIOPSIS) CEREA Carpenter. 

 Plate 37, fig. 6. 

 Cerithiopsis cerca Carpenter, Cat. Maz. Shells, 1857, p. 443. 



Shell small, broadly conic, semitransparent, light horn-color. 

 Nuclear whorls well rounded. Post-nuclear whorls separated by a 

 strongly channeled suture, marked by three spiral cords, the first of 

 which is a little anterior to the summit, the second median, and the 

 third a little posterior to the suture. In addition to the spiral cords, 

 the whorls are marked by axial ribs which equal the spiral cords in 

 strength. Of these ribs, 12 occur upon the first to third, 14 upon the 

 fifth and sixth, and 22 upon the penultimate turn. The junctions of 

 the spiral cords and the axial ribs form prominent tubercles, while 

 the spaces inclosed between them are elongated, oval pits on the early 

 whorls, having their long axes parallel to the spiral sculpture. On 

 the last volution they are rounded. Periphery of the last whorl 

 marked by a strong channel. Base moderately long, well rounded, 

 marked by three strong, spiral keels, of which the first is immediately 

 below the peripheral sulcus, and the second halfway between this 

 and the cord which surrounds the insertion of the columella. In 

 addition to the spiral cords, the base is marked by numerous, fine 

 incremental lines. Aperture irregular, very strongly channeled ante- 

 riorly; posterior angle obtuse; edge of outer lip rendered sinuous by 

 the external sculpture; columella moderately long, twisted, with the 

 edge reflected. 



Doctor Carpenter's type is on Tablet No. 2030, Liverpool collection, 

 British Museum, and was collected on Spondylus at Mazatlan. It 

 has seven post-nuclear whorls and measures: Length 2.4 mm., 

 diameter 1 mm. 



CERITHIOPSIS (CERITHIOPSIS) SOREX Carpenter. 

 Plate 37, fig. 2. 

 Cerithiopsis sorex Carpenter, Cat. Maz. Shells, 1857, p. 444. 



Shell minute, pupiform. Nuclear whorls three, smooth, well 

 rounded, forming a slender, mucronate apex. The first three post- 

 nuclear whorls increasing very rapidly in size, well rounded, orna- 

 mented with three spiral cords, of which the first is a little anterior 



