Fossil Mollusks From the John Day Basin in Oregon 



Ammonitella lunata (Conrad) 



Ten more or less imperfect specimens are in the University 

 of Oregon Collection. 



Pyramidula mascallensis Hanna 



Four imperfect specimens are in the collection. They exhibit 

 the very flat character of the whorls above in excellent manner. 



Oreohelix lecontei Stearns 



One specimen with four and a half whorls intact is in the col- 

 lection. At least one complete whorl has been lost. And the very 

 thin shell substance has been lost on all but the first three whorls. 



Helicina oregona n. sp. 



Plate 1, figures 3a, 3& and 3c 



Shell consisting of a little over six whorls with the sutures 

 between them but little impressed. Spire elevated and sides some- 

 what convex. Last whorl not depressed below the margin of the 

 one preceding. Spire covered with a thin layer of material which 

 is uniformly raised into ribs and of which there are nine or ten 

 to the millimeter on the last whorl. These ribs do not extend to 

 the base of the shell. Aperture oblique, about 45 degrees with 

 the axis. Outer lip reflected and thickened outside with callous 

 material. The columella makes a peculiar twist at its junction 

 with the base of the shell. This junction is slightly below the 

 level of the base when viewed spire down. There is no definite 

 carina at the margin of the body whorl. 



Measurements of type : greatest diameter 7.2 mm. ; least diame- 

 ter, 6.0 mm. ; altitude parallel to axis 4.5 mm. 



Type number 12, University of Oregon Collection from the 

 John Day Oligocene ( ? ) . No other specimens. 



The type is very well preserved and does not seem to be closely 

 related to any other known Helicina. The presence of the genus 

 in the Oligocene of the United States has not previously been known 

 and it is another instance of tropical forms which flourished much 

 north of their present range at that time. The ribbed surface of 

 the shell recalls H. rugosa of Jamaica and H. rugulosa of the 

 Society Islands but it is not in reality closely related to either of 



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