150" PHYSA. 



sometimes only one-fourth part of the length 

 of the shell; labrum very thin, advanced; la- 

 bium tumid, with a thin, loosely adherent 

 lamina. 



Animal of a very obscure light green color ; 

 whole surface of the body covered with oblong 

 dark spots ; foot shorter than the shell, lanceo- 

 late ; tentacles nearly white, rather long, very 

 slender ; mouth blood-red. Its motions are 

 exceedingly j-apid ; very timid, withdrawing 

 itself on the least alarm. 



Length 14, diam. 10 mill. 



Monmouth, Maine. 



No other authenticated locality has been 

 discovered, and it has been stated that the 

 species is Ph. heterostroplia, — the normal- 

 growth yielding to the inlluence of water sur- 

 charged with saw-dust from a neighboring 

 mill. Admitting the influence of the saw-dust 

 in causing the loose deposit of the labrum, I 

 still incline to consider it a very distinct spe- 

 cies. 



(m) 



