Descriptions of Neiv Species and N'eiv Varieties 227 



Helisoma campanulatum rideauense. New Variety- 

 Plat (> 109, fig.^. 21-24 



Shell very large, of five whorls, spire flattened, the inner whorls raised 

 slightly above the body whorl; sutures deeply marked. Base with three 

 to four whorls visible, rounded, in same plane, not reamed out as in dalli 

 and rudentis; sutures well marked and whorls rounded. Umbilicus small, 

 deep. Aperture as in campanulatum. Sculpture of heavy, evenly spaced 

 riblets, but not as heavy as in wisconsinense ; about as in some individual 

 shells of ca»ipanulatiuu. In the following table the measurements were 

 taken just behind the aperture, which is constricted and then dilated. 



H. c. rideauense differs from michiganense in the former's larger size, 

 smaller umbilical opening, and greater axial height. Surface is dull, not 

 shiny, caused by the heavy scul]:)ture. Color bright horn. The aperture is 

 more distinctly campanulate than in michiganense . 



Type Locality. Rideau River, Ottawa, Canada. 



Type Material. Five specimens, collected by F. R. Latchford, deposited 

 in the United States National ]\Iuseum, Accession no. 346627. Tlie holotype 

 is shown on plate 109, fig. 21 ; paratypes, figs. 22-24. 



GENUS Farapholyx 



Parapholyx effusa dalli. New Variety 



Plate 115, figs. 27-30 



Three whorls, rounded. Color greenish horn. Spire slightly raised, sutures 

 well marked, deep on last whorl. Sculpture of strong, erect, membranous 

 ribs, thirteen to fifteen on body whorl, equidistant or widely spaced. Very 

 fine lines of growth between ribs, spiral lines obsolete. Ribs usually absent 

 on spire whorls. The ribs produce spaced, vertical depressions inside aper- 

 ture. Aperture rounded, acute below. Columella narrow, concave, either 

 contpletely closing the umbilicus or leaving a small narrow and long chink. 

 A thin wash of callus on the parietal wall. 



Shell Greater Lesser Aperture Aperture 



Height Diameter Diameter Height Diameter 



4.9 5.0 4.8 3.9 3.3 Holotype 



5.0 5.0 5.0 4.0 3.3 Paratype 



5.0 6.0 5.0 4.1 3.2 Paratype 



Parapholyx effusa dalli differs from all other forms of the genus in the 

 presence of membranous ribs which stand up, either at an angle or verti- 

 cally, as leaf-like frills, very thin and easily broken off. The ribs in costata 

 and other costate forms of the genus (as costate specimens of klamath- 

 ensis from Klamath Falls) are simply rounded ribs, enlargements of the 

 lines of growth. These do not affect the inside of the aperture. In dalli, on 

 the contrary, the ribs appear as vertical creases on the inside of the aper- 



