VIVIPARA. 21 



it differs from that species in being much more incrassated and heavy ; 

 and although much decorticated and eroded upon the spire, the tip is not 

 truncated. In the labrum also is a distinctive character ; by comparison 

 this part will be perceived to be less arcuated in its superior limb than the 

 corresponding part in decisa. 



This shell is common in many parts of the Ohio as well as its tributaries. 

 In its full grown state it is very thick and ponderous, enlarging so much 

 in its body whirl, as to appear very different from the young shell. In 

 the early stages of growth it resembles P. decisa, Nobis, from which indeed 

 the back view would hardly distinguish it; but a sufficiently distinctive 

 character resides in the lower part of the labium, which in the decisa is 

 not obviously produced, whereas in the present species it is considerably 

 advanced, as in many species of Melania, to which genus it is closely 

 allied. (Saij.) 



Paludina ponderosa, Say, 1821, J. A. N. S. II, 173; Am. Conch. Ill, pi. 

 XXX, f. 1 ; ed. Binney, p. 68, 184, pi. xxx, f. 1. — Haldeman, Mon. p. 

 13, pi. iv (1840).— De Kay, N. Y. Moll. p. 86 (1843).— Deshayes in 

 Lam. ed. 2, VIII, p. 516 (1838) ; ed. 3, III, p. 455, excl. P. decisa.— 

 KilsTER in Chemnitz, ed. 2, p. 14, pi. iii, f. 1-4, p. 20, pi. iv, fig. 6. — 

 Soweeby, Gen. of Shells, f. 2.— Chenu, Man. de Conch. I. 310, fig. 

 2206 (Melantho) : Illust. Conch, pi. i. f. 14-15.— Philippi, Conch. 

 Ill, 3, pi. i, f. 16. 



There are microscopic revolving lines upon the whirls, and the 

 callosity at the superior angle of the aperture is sometimes devel- 

 oped sufficiently to make quite a fissure between it and the lip, 

 as in Lithasia. 



I have often received young specimens as Pal. regularis. 

 Other specimens are very difficult to separate from Viv. decisa. 



Paludina maxima, Ravenel (Cat.) may be this species. Xo 

 description was published. 



I have received specimens from Ohio, Indiana, Illinois, Michi- 

 gan near Lake Superior, Tennessee, and Alabama. 



A fac-simile in outline of one of Mr. Say's 

 figures is given (fig. 33). His figure of Pal. Fig. 34. 



decisa in the American Conchology seems 

 rather to represent this species (fig. 34). 



Haldeman mentions a var. A, "not exceed- 

 ing an inch in length ; the transverse wavy 

 striae are obsolete ; the spire is low, and trun- 

 cate-eroded, and the labium very much thick- 

 ened posteriorly, from the Alabama River." 



Dr. Showalter sent me numerous specimens 

 from the Coosa River. Paiudina decisa. 



