VIVIPARA. 29 
17. VIVIPARA SUBSOLIDA, Anthony. 
Plate 12, figs. 1, 2. 
Shell very thick, imperforate, ovate-elong- 
ate, spire much elevated, composed of 6—7 
convex whorls flattened somewhat superiorly ; 
aperture broadly ovate, about one-third the 
total length of the shell, parietal wall with a 
heavy callous deposit. 
Length 50, diam. 27 mill. 
Illinois, Iowa. : 
This is the most ponderous species of the 
fenus, being far heavier than V. ponderosa. 
It is sufficiently distinguished by its elevated 
spire and proportionally small aperture. Fig. 
2 represents a young specimen. 
18. VIVIPARA INCRASSATA, Lea. 
Plate 15, fig. 7, and Plate 14, fig. 6 (decapitata, Anth.) 
Shell smooth, decorticated, thin, imperforate, 
aperture small, oval, the parietal wall much 
(55) 
