VIVIPARA. 23 



Syn. Test, in 1834 prom. p. 39.— Haldeman, Mon. p. 15, pi. v (1840), 

 — DeKay, N. Y. Moll. p. 86 (1843).— Chend, Illust. Conch, pi. i, f. 

 18-19. 



Paludina heros, DeKay, N. Y. Moll. p. 85. 



Puludina subsolida, Anthony, Proc. Ac. N. Sc. Phila. 1860, p. 71. 



Helix dissimiiis, Wood, Ind. Suppl. pi. vii, f. 18 (1828). 



Lymnula ventricosa, Rafinesque, MSS. 



Ambloxis {Amblostoma) major, Rafinesque, MSS. 



Cochlea Virginiana Sj-c, Listek, Concli. t. cxxvii, f. 27 (1770). 



Petivee, Gazophyl. t. cvi, f. 18. 



Mr. Say makes no mention, in his description, of the minute 

 revolving lines which characterize the species. Fig. 35 is a fac- 

 simile of his figure 6, published in Nicholson's Encyclopedia, and 

 represents the true decisa. Fig. 34 is copied from the figure of 

 the American Conchology, which appears to me rather a small 

 specimen of Viv. ponderosa. It certainly has no truncated apex. 



The animal of this species is given in figure 18, copied from 

 Haldeman's Monograph. 



In many specimens there is a thickening as in Lithasia, which 

 is also often present in individuals of Viv. ponderosa. Among 

 the curious abnormal forms which have come under my view, and 

 which seem referable to V. decisa, or the form called integra, are 

 some on which the columellar callus is not appressed in its whole 

 breadth to the body whirl, but, standing out from it, makes the 

 peritreme almost continuous. No. 8903 of the collection has a 

 revolving band ; No. 8871 is reversed, which is rare in adult spe- 

 cimens, though the young more frequently furnish examples of it. 

 One has the aperture 20 and the entire shell 45 mill, long, the 

 suture deeply impressed, the whirls below it abruptly shouldered, 

 the shoulders of the upper whirls worn away so as to make the 

 top of each whirl completely flat and forming almost a right 

 angle with its sides. In globoseness or narrowness, 

 of the whirls it is extremely variable. -^^S- ^'^- 



To the kindness of Dr. James Lewis I am in- 

 debted for the opportunity of figuring several 

 shells which appear to be abnormal forms rather 

 than constant varieties. (Figs. 36, 37.) 



I have drawn up the synonymy of this species 

 after a careful study of a large number of indi- 

 viduals from numerous different localities. The vmi jara decua 

 Smithsonian series alone is derived from fifty deformed. 



