PHYSA. 



89 



Fig. 153; 



Physa fragiliS; Mighels. — Shell very thin and fragile, translucent, 

 horn-color, obliquely ovate ; whirls four ; last whirl campanulate, suture 

 deeply impressed at the enlargement of the last whirl ; spire 

 usually less than one, sometimes only one-fourth part of the 

 length of the shell ; labrum very thin, advanced ; labium 

 tumid with a thin, loosely adherent lamina. Length, .55 inch ; 

 greatest breadth, .4 inch ; divergence, 900. 



Animal of a very obscure, light-green color ; whole surface 

 of the body covered with oblong dark spots ; foot shorter than 

 the shell, lanceolate ; tentacles nearly white, rather long, very 

 slender ; mouth blood-red. Its motions are exceedingly rapid ; 

 very timid, withdrawing itself on the least alarm. It is very tenacious 

 of life, at least it is not easily starved. Three specimens are now before 

 us in a tumbler of water, November 10th, where they have remained since 

 the first of July. The water has not been changed more than half a dozen 



