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PROCEEDINGS OF THE NATIONAL MUSEUM 



VOL. 102 



ally disappear, allowing split beads to re-fuse into a single row. Many 

 exceedingly fine, incised lines rarely may be present between the rows 

 of beads. Axial sculpture consists of fine, irregular lines of growth 

 which may be prominent, especially in last whorl, at various distances 

 behind lip. Some specimens show a few rather regular, but very 

 small pimplings. In general, the variations mentioned above may 

 appear or disappear at random throughout ontogenetic development. 

 Aperture oblique, moderately ovate to elongate, with a length about 

 one-third that of entire shell. Parietal wall glazed with a transpar- 

 ent, thin covering of shell matter. Columella short, slightly arched, 

 rounded within aperture but sharp on its outer and lower edge. Um- 

 bilicus absent. Outer lip thin, sharp, and projecting forward at its 

 center portion. Interior of aperture glossy, chalky white. Perio- 

 stracum covering entire outer shell (except for parietal wall and colu- 

 mella) thin, closely cemented to shell, yellowish brown. It is most 

 frequently worn away at spire and regions overlying the more promi- 

 nent beads. Inlaid in the shell itself there are a few small, squarish 

 color-blotches of red-brown, which are usually more easily seen in 

 younger specimens than in adults. 



Description of a newly born specimen (pi. 9) : Length 2.0 mm., 

 width 1.0 mm. Nuclear whorls rosy pink, finely granulated. Total 

 number of whorls 4.5. Spiral sculpturing in postnuclear whorls con- 



Tablb 1. — Measurements of shells from Geus River, Guam Island 



