OP CONCHOLOOY. 127 



at Washington, and more abundantly the Roanoke River and Shenandoah 

 River. Figs. 37 — 41 represent variabilis, Lea, another form having the 

 same distribution as the last. Fig. 42 is trivittata, DeKay, being the same 

 form, rarely banded, from Lake Champlain. 



The transition from a smooth to a toothed columella is represented by 

 figures 43 — 49, exhibiting forms of nigrescens, Conrad. A. monodontoides, 

 Con. fugs. 50 — 53), A. dentatus, Couthouy ("figs. 54, 55), and A. affinis, 

 Hald. (fig. 56), are all forms having the toothed columella. The habitat of 

 the latter is most probably erroneously given as Ohio. 



9. A dilatata, Con. Figs. 57 — 78. Subovate, moderately 

 thick; spire conical, somewhat elevated, suture well impressed; 

 whorls 4 — 5, the last large, inflated, generally smooth, some- 

 times angulated in the middle, or with several angles, or 

 closely covered by revolving ribs ; aperture large, round- 

 ovate, dilated at the base, and produced towards the left, co- 

 lumella straight, occasionally toothed. Light brown to bright 

 or dark green. Rivers of Western Virginia tributary to the 

 Ohio River. 



Another protean species, replacing dissimilis, Say, from which it is con- 

 stantly distinguished by the peculiar forua of the base of the aperture. 



Figs. 57 — 59 represent the typical shell. Fig. 60 is a young banded spe- 

 cimen, with a toothed columella, the type of A. Bogersii, Con. Fig. 61 is 

 carinatus, Anth., and 62 and 63 Kirtlattdianus, Anth. 



Fig. 64 represents inflata, Lea, seemingly very distinct, but connected 

 with the type form by insensible gradations ; and fig. 65 is A. litturina 

 Hald. 



The following represent Haldeman's "Varieties:" Figs. 66, 67, glauca 

 fig. 68, solidula, fig. 69, sinuata, fig. 70, striata, fig. 71, rapatformis. The 

 balance of the figures illustrate a series of specimens, many of which some- 

 what resemble dissimilis. 



As this species becomes old, the base of the aperture sometimes thickens 

 and loses its dilated angle, so as to appear, when thus abraded, to be 

 broadly rounded below. 



10. A. corpulenta, Anth. Fig. 79. Broad-ovate, smooth, 

 thick ; spire conical, suture slightly impressed ; whorls 5 — 6, 

 flattened, the last very large, inflated, subangular on the peri- 

 phery ; aperture large, ovate, broadly rounded below, colu- 

 mella incurved. Dark brown, sometimes banded within JSf 

 Car. 



A larger, more ponderous species than dissimilis. But it may be only a 

 variety of that shell. Occasionally one or more additional angles on the 

 body whorl are visible, and, as previously mentioned, I suspect that A. 

 canalifera is the juvenile form, with the angles better developed. 



11. A. melanoides, Con. Figs. 80 — 82. Conical, thick; 

 spire short conical, suture moderately impressed ; whorls 4 

 flattened, the last large ; aperture elliptical, angular at base, 

 about half the length of the shell. Light green, obscurely 

 banded. N. Ala. 



Fig. 82 represents the adult, A. turgida, Hald. 



12. A. trilineata, Say. Figs. 83—85. Subglobose, rather 

 thin ; spire short, apex sharp, suture well impressed ; whorls 

 4, rounded, the last large ; aperture round. Yellowish-brown, 

 with generally three dark-brown revolving bands. Ohio Riv. 



Fig. 85 is A. viridis, Lea, an adult shell without bands. 



