PHYSA. 



127 



Typical species. 



I. Species Inhabiting the Pacific States. 



A. Smooth species. 



1. PHYSA LORDI, Baird. 



Plate 6, fig's. 1, 2. 



Shell thin, quite large, corneous, tumid, 

 gibbous, aperture large, outer lip acute ; ex- 

 ternal surface very minutely decussated; 

 whorls six, the first two minute, tinged with 

 black, the last swollen, four times the size of 

 the others. 



Length 19 to 25, diam. 12 to 19 mill. 



This species is one of the largest of the 

 genus, and is much swollen and gibbous. 



Lake Osoyoos, British Columbia ; Washing- 

 ton Territory ; Humboldt Lake, Nevada. 



In his remarks upon this species Professor 

 Baird states that Physa heterostropha, Say, 

 " abounds in the Sumass Prairie on the Fraser 

 River ;" but he has mistaken some other spe- 

 cies for it, as Ph. heterostropha has not yet 

 (43) 



