«4 



more tapering spire and a narrower aperture. Otherwise they 

 are much alike. This is one of the most active and M'idely dis- 

 tributed of the species taken. It is said sometimes to attack and 

 devour insects as large as itself. The eggs are deposited, accord- 

 ing to Say, in the month of May, but probably at intervals dur- 

 ing the summer also. Egg masses, which in all probability were 

 from this snail, were quite frequently found attached to the out- 

 side of shells, where they had been left by other individuals. 

 The shells were frequently clothed with growths of stalked 

 infusorians. 



Localities: Harkness Slough, Quincy Bay, Willow Slough, Cedar 

 •Creek, Wood Slough. 



Helisoma irivolvis, Say. 



{Plcmorhis irivolvis, Say, Am. ed. Nich. Enc, pi. ii, f. 2, 1817, 

 1818, 1819.) 



Common in many of the pools. Easily recognized by its de- 

 pressed shell, — the whorls lying nearly in one plane so that they 

 can be followed on two sides of the shell. Large examples taken 

 measure five eighths of an inch in diameter. 



Localities: Harkness Slough, Willow Slough, Lily Lake, Long 

 Lake, Wood Slough. 



Family Valvatid.e. 



Valvata tricarinata, Say. 



(Cyclostoma tricar inata, Say, Jour. Acad. Nat. Sci. Phil., i, 13, 

 1818.) 



This small mollusk was common in many of the pools, but was 

 not often brought out in the nets from pools in which it was very 

 abundant. The shell is about .20 inch in diameter and may be 

 recognized at once among our species by the strong ridges on the 

 outside of the shell. It is somewhat depressed and the aperture 

 is nearly circular in outline. The food is said to be vegetable 

 matter. The eggs of related European species are deposited 

 singly. 



Family Viviparid^. (Rivee Snails.) 



Vivvpara intertexta, Say. 



{Faludina intertexta, Say, New Harmony Disseminator, ii, 2-14. 

 1829.) 



A common and uniformly distributed snail of rather large size. 

 Shell rather stout, with about five strongly convex whorls. Adults 

 dull reddish brown in color; young paler, with numerous fine 

 revolving strijio on the whorls. The largest example taken 

 measures one inch in length, with the largest whorl .87 inch in 

 diameter. Inside the aperture may usually be seen several large 

 reddish brown revolving bands. The young are born alive. 



