28 University of Washington Publications in Geology [Vol. I 



the angle of the whorl and the suture there are two revolving ribs on the penulti- 

 mate whorl and three revolving ribs on the body whorl, below the angle of the 

 whorl four revolving ribs occur, all cut by radiating striae which give the sculp- 

 ture a nodose or beaded appearance; base of the body whorl has revolving ribs 

 less pronounced than on the rest of the shell; umbilicus deep, moderately wide 

 for the size of the shell, interior and margin beaded by radiating striae; where 

 portions of the outer layer of shell material has been peeled off a nacreous inner 

 layer is revealed. 



Dimensions. Co-types measuring respectively; altitude 2.25 mm., 4 mm.; 

 width of body whorl 4 mm., 5.25 mm. 



Occurrence. At locality 326 (University of Washington Palaeontological 

 Collection) on Olequah Creek, back of Armstrong place about one-half mile 

 north of Vader, Lewis County, Section 29, Township 11 North, Range 2 West, 



CRESCENTENSIS n. sp. 



Plate XII, Figure 11 



Description. Shell small ; whorls four, rounded ; suture impressed, slightly 

 channelled ; aperture round ; surface of the whorls ornamented with prominent, 

 revolving ribs crossed by radiating lines which dissect the revolving ridges into 

 nodes or beads. This sculpture extends with equal prominence over the whole 

 surface of the whorls and umbilical area. 



S. crescentensis differs from S. olequahensis in the lesser angulation of the 

 whorls and in the strength of the beaded sculpture. The revolving ribs on the 

 base of the body whorl of olequahensif are 1 much smaller and less noticeable than 

 on the upper surface of the whorls and they are only crossed by faint lines, while 

 in S. crescentensis the basal sculpture is as strongly developed as elsewhere ; al- 

 together in 5. crescentensis there are eleven, revolving ribs including- the rib which 

 forms the margin of the umbilicus. 



Dimensions. Altitude 4 mm. ; width of body whorl 5 mm. 



Occurrence. At locality 358 (University of Washington Palaeontological 

 Collection) at Joice station, about one-fourth mile east of Tongue Point R. R., 

 Port Crescent, Section 22, Township 31 North, Range 8 West. 



GENUS NERITA UNNE 



NERITA WASHINGTONIANA n. sp. 



Plate XI, Figure 4 



Description. Shell small, semi-globose ; spire minute absorbed by the body 



