Fossil Freshwater Mollusks from Oregon 



DESCRIPTION OF SPECIES 



GENUS: PLANORBIS MULLER 



SECTION PARAPLANORBIS HANNA, NEW SECTION 

 Whorls rounded on the periphery as in Helisoma Swainson but 

 aperture not expanded, umbilicus very narrow and size minute. 

 Type, Planorbis (Paraplanorbis) condoni Hanna, new species. 



PLANORBIS CONDONI, N. SP. 

 Plate 1, figures 1, 2, and 3 



Shell, planorboid, composed of about 4^ regularly increasing 

 whorls; apical cavity a cone of about 120 degrees. Last whorl 

 slightly angulated about the upper margin and descending slightly 

 at the aperture. Lines of growth fine and even, giving the shell a 

 silky luster. Umbilicus deeply rimate, .51 mm. in diameter. Aper- 

 ture roughly triangular but rounded on the outer lip ; not expanded 

 or thickened but a depression both above and below the periphery. 

 Diameter, 2.67 mm. ; altitude, .35 mm. 



Type, No. 14 University of Oregon. Cast of same No. 671, 

 Mus. California Acad. Sci. 



Type from University of Oregon, Locality 212. Vicinity of 

 "Warner Lake, eastern Oregon. Pliocene. 



This little shell is unlike any other known to me; it could not 

 even be placed in any of the sections of the genus Pldnorbis as 

 defined by Dall, a late summarizes 2 In the narrow, deeply reamed 

 umbilicus it resembles the section Hippeutis Agassiz, but the whorls 

 are not planulate on top or carinated on the periphery. No lamellae 

 were found in the aperture, thus excluding it from the genus Seg- 

 mentina which it somewhat resembles. 



The species is not common, only three specimens having been 

 found in the deposits about Warner Lake. These display almost 

 no variation from the type described above, except in being some- 

 what smaller and younger. 



PLANORBIS (TORQUIS) SCABIOSUS, N. SP. 



Plate 1, figures 4, 5 and 6 



Shell similar in size and shape to Planorbis parvus Say, but has 

 more whorls for the same size. Whorls increase in size less rapidly 

 and they are more nearly circular in cross section. The apex is 

 slightly depressed below the plane of the whorls. Last whorl not 

 depressed at the aperture and aperture not expanded. Umbilicus 

 regularly formed, a little narrower in shells of the same size than in 

 P. parvus. The most conspicuous difference is in the lower margin 

 of the aperture. In P. scabiosus this leaves the junction of the 



2 Ball, W. H. Harriman Alaska Exp., Vol. 13, p. 80, etc. 1905. 



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