74 



1003 Planorbis anitensis Cp. 



"Shell (when held mouth downward) with the right side con- 

 cavo-convex, the left flat (or slightly concave), the left margin 

 forming a sharp carina expanded beyond the edge of shell, which 

 is marked by a compressed line. Whorls 5, visible on both sides, 

 uniformly flat on the left side, forming a concave umbilicus on 

 the right, where their surface is founded. Mouth triangular, the 

 right lip arched, the left nearly flat, the extremities joined to 

 outer angle and to obtuse margin of umbilical cavity. Umbilicus 

 half as wide as the shell; flat side of mouth one-fourth of diam- 

 eter; greatest breadth (at mouth) over one-fifth of same; greater 

 diameter 0.26, least 0.03 inch." — Cooper, Cal ac pr 2d ser, 3:341. 



Type locality: Laguna at Santa Anita, Baja California, at an 

 elevation of 100 feet, and 10 miles from San Jose del Cabo. 



1004 Planorbis deflectus Say. 



Great Slave lake to Virginia, Nebraska, and Montana. 



1005 Planorbis exacutus Say. 



Maine to Virginia, west to Kansas, Montana, and Vancouver 

 Island. 



1006 Planorbis gracilentus Gould. 



Colorado desert, California? — Texas — Mexico. 



1007 Planorbis hornii Tryan. 



Shell of three convex volutions; aperture almost orbicular, not 

 oblique, nor extending above or below the plane of the whorls; 

 labrum slightly reflected, thickened within, its ends converging so 

 as nearly to connect on the parietal wall; lines of growth fine and 

 close. Color light horn. Diameter 21, height 7 mm. 



Living: Fort Simpson, British America (George H. Horn). 

 Grant's lake, California (W. M. Gabb). 



1008 Planorbis opercularis Gould. 



Shell dextral, much depressed, lenticular, with a prominent 

 blunted keel at compressed line; tip sunken; beneath the periph- 

 ery defined by a marginal, umbilicated for about one-third the 

 breadtli of the base, showing 3 volutions, convex, surface rather 

 rude and indented, marked with irregular, coarse, much arcuated 

 lines of growth, and here and there a few obscure, raised revolv- 

 ing lines; color dark chestnut brown, a little clouded; whorls 

 above 4, slightly convex; suture well defined, impressed; aper- 

 ture transversely subrhombic, lip above slightly acute-angled, be- 

 neath arched, lips embracing % of that part of the whorl which is 

 beneath the carina. Diameter 6, height 1.5 mm. 



Living: Common in the waters of California. Vancouver Isl. 



1009 Planorbis peninsularis Cp. 



"Shell with both sides concave, the right with whorls rounded, 

 their edge forming an obtuse margin, and the outer one partly 

 enclosing the others so that it forms two-thirds the greater diam- 

 eter of the shell. Whorls 5, visible on both sides, the rounded (or 

 right) surface showing less of them than the other. Left (or 

 umbilical?) surface nearly flat, deeply concave near middle, the 

 umbilicus being over one-third of diameter. Mouth trapezoidal, 

 very oblique, its lips curved, the right extremity attached near 

 the concave spire, the left to the obtuse periphery of shell. Mouth 

 one-third longer than wide; its breadth over one-third that of 

 shell. Greater diameter 0.16, least 0.05 inch. Color brown, sur- 

 face smooth." — Cooper, Cal. ac pr 2d ser, 3:342. 



Type locality: — "With P. anitensis, in same laguna." 



1010 Planorbis subcrenatus Cpr. 



Shell tumid, very thin, horn-colored; whorls 6, rounded, su- 

 tures impressed; with sharp radiating, somewhat crowded and 

 occasionally minutely crenulated ridges; aperture rounded, pari- 



