The Nautilus. 



Vol. III. SEPTEMBER, 1889. No. 5. 



NOTES ON PHYSA TRITICEA OF LEA ; ITS RELATIONS AND COMMENTS 

 ON THE VARIATION. Etc., OF PHYS^. 



BY ROBERT E. C. STEARXS. 



THIS California pond snail was described by Dr. Lea in 1X.56, 

 from specimens collected by the late Dr. John B. Trask, in 

 Shasta Conuty. It was afterwards collected by Dr. J. G. Cooj^er 

 inferentially in "South and East Oregon," as he adds these locali- 

 ties in his " Geographical Catalogue " to that previously given. In 

 May, 1883, and subsequently, I detected it in springs in the vicinity 

 of Auburn, in Placer County, at an elevation of about 1,300 feet, 

 and collected at first between sixty and seventy specimens, sub- 

 sequently more. It seems rather to have escaped the attention of 

 collectors ; or if found, has perhaps been labeled under some other 

 name ; as like nearly all, if not all, of the alleged species of Physa, 

 it exhibits more or less variation when numbers of individuals are 

 compared, even when such individuals are a part of the same colony. 



The form to which Dr. Lea gave the name of triUcea is, on the 

 whole, rather persistent, and adheres quite closely to the type, as 

 given in Binney ^(figure 160) ; it is thirty-four hundredths (.34) 

 of an inch in length. My specimens of the same length agree 

 closely and generally with the figure, though the larger individuals, 

 forty-six hundredths (.46) of an inch in length, exhibit some differ- 

 entiation in the twist of the columella when compared with the 

 smaller ones. 



The largest are. hardly typical, and though collected very near 

 (within a half mile of) the smaller and more nearly typical forms, 



* L. and F. W. Shells of North Arr erica, Pari II, p. 94; S. I. Coll., No. 143. 



