PHYSA. 131 
6. PHYSA OCCIDENTALIS, Tryon. 
Plate 6, fig. 18. 
Shell with well-rounded whorls, suture im- 
pressed; spire moderate, sometimes short; 
apex acute; texture rather thin, surface 
crowded with growth-lines, polished, amber- 
colored; aperture moderately large, outer lip 
well rounded, thickened within and tinged 
with red; columella white, indented, some- 
what folded, sharp-edged, curved to the right 
and forwards into a sort of beak at the base. 
Length 18, diam. 11 mill. 
California, Oregon. 
This species, widely diffused throughout the 
Pacific States, appears to replace the eastern 
Ph. heterostropha, with which it has been 
generally confounded. It may be readily dis- 
tinguished from that shell, however, by the 
very different form of the columella; so pro- 
foundly indented above, and so sharp, twisted 
and curving forwards towards the base. 
(47) 10 
