28 VIVIPARA. 
* * Shell elongate-conical, green. 
16. VIVIPARA DECISA, Say. 
Hald., p. 4, t. i, p. 10, t. iii (inéegra). 
Plate 12, fig. 8 (deformed). Plate 12, fig. 9 (reversed). 
Plate 13, fig. 5 (Paludina Milesii, Lea). 
As indicated above by the references to fig- 
ures, I consider V. integra to be identical 
with V. decisa. The principal differences are 
that the former attains a larger size and the 
tip ef the spire is never eroded; but the same 
differences occur in Lioplax subcarinata, the 
specimens from the western waters being uni- 
formly larger, more perfect in the spire, and 
more solid. Paludina Milesw, Lea, I cannot 
separate as a species, as it does not exceed the 
usual range of variation in form of V. decisa. 
Massachusetts to Iowa, and southwards to 
Alabama. 
(54) 
