IDO CALIFORNIA ACADEMY OK HCIKNCES. 



roiinclecl at periphery; siiliire very deep, tin- wliorl'- slo|)in)i; toward it; liase cup-shaped, exhibiting 

 all of till' whorls; apfrturt- cxliihiting a viry ol)li(|iic section of a cylintlcr; slightly expanded, em- 

 bracing ahoiit one-hall the height oT the last wlunl, and joincti by callus. 

 Dinifiisions. — Alt. 6 mm.; maximum diam. 11.5 nun. 



S|)ooiiiioii.s idi'iitiliod liy Dr. Dull. 



Kan- in tin- ii|i|h r mihI lower S.m I'cdro series at San Pedro; three specimens. 

 Tlie speciriien fijjjiiri'd is lioni the upper San l\'dr() series at San I'edro, and is now 

 in llie collection of Delos ArnoUl. 



Liriitg. — Interior of Oregon ((Joiild). 



Pleistocene. — San Petl ro (Arnold). 



Family XIA'll. rilVSID.K. 



Genus Physa DrajKinKdid. 

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



Phijsd fontinalia Linn, is a characteristic species. 



158. Physa heterostropha Snij. 



/V/)'i(j //f/^;<75//o^/ia Say, Nicholson's Encycl., PI. 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 S mm.; defi. 

 95 degrees. 



This fresh-water form, toi^ether with several other s])ceies having the same 

 ]ial)itat, was found in the lower San Pedro heds at San Pedro. There is no douht as 

 to their occurrence in these marine deposits, into which they were probably washed 

 i)y -ome fresh-water stream. 



Living. — North Amefica. 

 Pleistocene. — San Pedro (Arnold). 



Supcrfamily DITREMATA. 



Family XLVIII. AURICULID^. 



Subfamily MELAMl'lS.K. 



Gentis Melampus Monffori. 



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 cliaracteristic species. 



