196 CALIFORNIA ACADEMY OF SCIENCES. 



rounded at periphery; suture very deep, the whorls sloping toward it; base cup-siiaped, exhibiting 

 all of the whorls; aperture exhibiting a very oblique section of a cylinder; slightly expanded, em- 

 bracing about one-half tiie height of the last whoil, and joined by callus. 

 Dimejisions. — Alt. 6 mm.; maximum diam. 11.5 mm. 



Specimens itleiitified by Dr. Dall. 



Rare in the upper and lower San Pedro series at San Pedro; three specimens. 

 Tlie specimen figured is from the upper San Pedro series at San Pedro, and is now 

 in tlie collection of Delos Arnold. 



Livincj. — Interior of Oregon (Gould). 



Pleistocene. — San Pedro (Arnold). 



Family XLVII. PHYS1D.E. 

 Genus Physa Drap<irnaud. 

 Shell ovate, sinistrally spiral, thin, polished; aperture rounded in front. 

 Physa fontina lis Linn, is a chai'acteristic species. 



158. Physa heterostropha Say. 



P/ijsa //e/ffosOvp/m Say, Nichohon's Encyc]., PL LXIX, fig. 6. Cpr., Brit. Assn. Rept., 1863, 

 p. 674. Keep, West Coast Shells, p. 118, fig. 107, 1892. 



Shell small, sinistral, shining, pellucid; whorls five ventricose; suture distinct; aperture 

 oval; outer lip thin; pillar lip strong and forms a conspicuous sinus where it joins the whorl above. 



Dimensions. — Long. 12 mm.; lat. 7 mm.; body-whorl 10 mm.; aperture 8 mm.; defl. 

 95 degrees. 



This fresh-water form, together with several other species having the same 

 habitat, was found in the lower San Pedro beds at San Pedro. There is no doubt as 

 to their occurrence in these marine de])Osits, into which they were probably washed 

 by some fresh-water stream. 



Living. — North America. 

 Pleistocene. — San Pedro (Arnold). 



Supcrfamily DITREMATA. 



Family XLVIII. AURICULID^. 



Subfamily MELAMPIN^. 



Genus Melampus Montfort. 



Shell oval-conoidal, or suboval, solid; spire rather short; aperture elongated, narrow; 

 columellar lip with several dentiform plications; columella plicate; outer lip sharp, interior with 

 revolving ridges. 



Melampus luteus Quoy is a characteristic species. 



