Pyramidellidae 121 



width, next above is a second beaded spiral of size almost equal to 

 the first, next a narrower interspace and a third, smaller beaded 

 spiral immediately adjacent to the suture. Axial ribs over each whorl 

 cross the interspiral spaces and extend as radii over the rounded base. 

 A strong fold from the top of the columella is continued around base 

 of shell to form the lowest crenulation of outer lip. Aperture ovate, 

 outer lip sharp, crenulated by external sculpture, three internal lirae; 

 operculum pale yellow, animal white. 

 From three to six fathoms. 



Genus ODOSTOMIA Fleming, 1817 

 Odostomia-i- aeutideiis Dall PI. 46, fig. 321 



Alt., 4; alt. of spire, 1.6 mm. Shell yellowish white, glossy, solid, 

 pyramidal with aperture extended beyond base; apex acute; five 

 or six rounded whorls, base of body whorl rounded; sutures defined 

 but not channeled; whorls without sculpture save for growth lines; 

 aperture entire; outer lip sharp, rounded into columella below; 

 columella distinct with polished callus above, one sharp, horizontal, 

 almost median tooth; a groove posterior to columella but no umbili- 

 cus. 



This Odostomia is not common; it inhabits muddy flats. 



Subgenus MENESTHO Moller, 1842 

 Odostomia bisnturalis'-is Say PI. 23, fig. 161 



Alt., 4; alt. of spire, 3 mm. Shell elongate, conic-pyramidal, 

 base extended; milky white; thin pale-brown epidermis; apex of 

 about two whorls partly embedded in first postnuculear whorl; seven 

 or eight flattened whorls, shouldered at sutures; sutures well de- 

 fined. A strong, deeply cut spiral, parallel with suture, is engraved 

 on upper portion of each whorl. Aperture oval, upper angle acute, 

 base rounded into slender columella which has one oblique fold well 

 within aperture; operculum corneous, brown. 



Inhabits muddy sand flats. 



21- Gr., odon, odontis, tooth; stoma, a mouth; Lat., acutus, acute; dens, 



tooth. 

 -13 Lat., bis, twice ; sutura, sew or stitch — seam. 



