'2Q 



labium without much fold ; color yellowish horn, with 

 frequently, bands of white ; aperture reddish within ; 

 hMigth 14 mill. 



OK.^IIS raiYSA, DiiAP. 



The Physas are tlie most active and hardy of all the 

 aquatic univalv(?s. They move rapidly through the 

 water shell downwards. They inhabit muddy bottoms 

 and prefer still waters. They are tenacious of life, liv- 

 ing much longer out of water than any other species I 

 have tak(>n, and emitting when removed from their 

 native element, a peculiar snapping noise. I have seen 

 them attack bugs as large as themselves with the 

 greatest ferocity and quickly draw them beneath the 

 water. The shells are sinistral. In regard to their 

 l^ropagation, a curious fact came to m}'^ notice about 

 two years ago. Quite a large stream of water was 

 allowed to How from an artesian well in Central Park, 

 (which is situated in the city of Chicago,) oft* through 

 the prairie in a southerly direction. For a tiuK^ there 

 was no appearance of shell life in this stream ; but 

 presently I noticed the form Physa gyrlna in great 

 abundance. How they got there was the question, as 

 there was no means of communication with other 

 waters except through the artesian well before men- 

 tioned. And as this and other similar wells in the 

 vicinity are, without doubt, subterraneously supplied 

 from our Lakes, these Physas must have come 

 through with the current. ls\^' friend, Dr. James 

 Lewis, offers this solution of the question :— that the 

 eggs were deposited in the lake and drawn into the 



