heterostropha Binney, (except synonym) L. & F. W. Shells N. 

 Am. II, 1865, 84, fig. 144; P. Wolfiana Lea, -lour. Phila. Acad. 

 Nat. Sci., VIII. 1874, 63, PL XXI. 20; :;: P. heterostropha Hanni- 

 bal, W. Coast Shells. L910, 311, fig. 297. 



In the new edition of "West Coast Shells" the writer ex- 

 pressed the opinion that the West American Physas with the 

 exception <>l' hypnorum, ;i boreal species round west of the 

 Rocky .Mountains at hut a few points, were all referrable to 

 Physa heterostropha and P. heterostropha osculans, the former 

 aorthern, the latter southern in distribution. Further studies 

 have in nowise altered these views, hut an examination of a 

 considerable series of European Physas has shown conclusively 

 that heterostropha is not distinguishable from P. fontinalis of 

 northern Europe, while the only safe way to separate heteros- 

 tropha osculans and P. fontinalis acuta of the Mediterranean 

 region is by the difference in locality. Since fontinalis and its 

 subspecies were named years earlier, the law of priority re- 

 quires their use in preference to the American names. 



Southern California is rather beyond the range of typical 

 fontinalis which is uncommon south of the latitude of Monte 

 rey Bay. The Physas from this region are referrable to the 



following subspecies. 



Northern Europe; northern North America south to Vir- 

 ginia and middle California, infrequently beyond. 

 Physa fontinalis acuta (Draparnaud). 



Physa acuta Draparnaud, Hist. Moll. Fr., 1805, 55, PI. Ill, 

 10-11; P. osculans Ealdeman (restr.) Mon. Lim. VI, 184:5, PL 

 II, 13; P. mexicana Philippi in Martini & Chemnitz, 1844, 5, Tab. 



I, fig. 3-4; P. humerosa Could. Proe. Bos. Soc. Nat. Hist., V, 

 1855, 128; P. virgata Could, Loc. cit. 1855, 128; P. Traskii Lea, 

 Proe. Phila. Acad. Nat. Sci. VI, 1856, 163, PL XXIV, 80; P. 

 Gabbi Tryon, PrOc. Phila. Acad. Nat. Sci., 1863, 14<>, PL I, 14; 

 :;: P. osculans Binney, (in synonymy) L. cV; F. \Y. Shells N. Am., 



II, 1865, 85, fig. 146; *P. heterostropha osculans Hannibal, AY. 

 Coasl Shells. L910, 312, PI. Ill, 17. 



The straight pillar which distinguishes this subspecies 

 from typical fontinalis need not be looked for in specimens less 

 than ten millimeters in length which are not full grown. The 

 character appears only in the adult shell. 



Physa is without exception the most widely and abundant- 

 ly distributed fresh-water mollusk in southern California. No 

 stream, pond, or swamp outside the highest mountains is with- 

 out it. It is capable of thriving in moist situations flooded but 

 three or four months a year, though unlike the Calbas it is not 

 active excepl when at least partially submerged. 



.Mediterranean region and central Europe; North America 

 from Pennsylvania and northern California to southern .Mexico 

 and West Indies. Along northern limits it overlaps and inter- 

 grades with preceding Physa. 



29 



