1918] J'aii Winkle: Paleontology of the Oligocene 8J> 



GENUS HEMIFUSUS SWAINSON 



HEMIFUSUS ARNOLDI n. sp. 

 Plate VII, Figure 11 



Description Shell minute, slender and moderately thick; whorls seven in 

 number ; suture distinct, appressed and sinuous ; upper surface of body whorl concave ; 

 spire about equal in length to body whorl and canal; whorls sharply angulated 

 about one-third the distance below the suture line; surface of whorls decorated 

 by 13 prominent longitudinal ribs which become obscure on the posterior surface 

 of the body whorl ; these are crossed by six prominent, rounded revolving ribs ; 

 surface of whorls above the angle ornamented by four small revolving ribs with 

 interspaces of triple width. On the angulated portion of the whorls somewhat 

 prominent nodes are formed by the intersection of the longitudinal and revolving 

 ribs ; body whorl ornamented by 1 8 prominent, flat-topped revolving ribs which 

 progressively become less developed toward the end of the canal; between these 

 are interspaces of double width which contain no revolving threads ; outer lip 

 moderately thick; inner lip slightly calloused; aperture elongate-elliptical; canal 

 short, broad and slightly reflected to the left. 



Dimensions Altitude of shell 6 mm.; altitude of spire 3.5 mm.; maximum 

 diameter of shell 3 mm.; angle of spire 35. 



Occurrence At locality 330 (University of Washington Paleontological Col- 

 lection) situated at the Greece ranch, four miles east of Vader, on the east bank of 

 Cowlitz River, in Section 25, Township 1 1 North, Range 2 West. 



Horizon Lower Oligocene ; lower phase of Molopophorous lincolnensis Zone. 



HEMIFUSUS LINCOLNENSIS n. sp. 

 Plate VII, Figure 10 



Description Shell of moderate size and moderately convex; whorls seven in 

 number and slightly angulated; upper surface of body whorl above the angle 

 moderately concave; middle portion strongly convex and merging into a sharply 

 sloping base; the upper portion of the surface of the whorl develops into a collar 

 which comes in contact with the whorl above along a well developed suture line. 

 Surface of whorl ornamented by 13 well defined longitudinal ribs which are present 

 on all of the whorls but are confined to the middle portion of each; they disappear 

 entirely on the upper and lower thirds of the surface; they are crossed by numerous 

 well defined revolving ribs and intervening threads; two well marked ribs are present 

 on the collar just below the suture; eight nearly square topped, moderately well 

 defined lines ornament the upper third of the surface of the body whorl; these are 

 equally spaced and equally developed ; they are separated by interspaces of double 



