28 VIVIPARA. 



* * 



Shell elongate-conical, green. 

 16. VIVIPARA DECISA, Say. 



Hald., p. 4, t. i, p. 10, t. iii (integra). 



Plate 12, fig. 8 (deformed). Plate 12, fig. 9 (reversed). 



Plate 13, fig. 5 (Pahdma Ililesii, 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 of the s]3ire 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 Milesii, 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) 



