24 Calvin Goodrich 



Operculum: Very thin, reddish, 5 mm. in altitude, 3 mm. in diameter. Lines of 

 growth fine, interrupted by occasional heavier lines which give the operculum the 

 appearance of an opening fan when viewed bj' transmitted light. Left margin slightly 

 curved, right margin broadly curved, thin and torn. Apex acute. Polar point, crater 

 like, somewhat large for so small an operculum ; it is located on the left margin 

 about I mm. above the base. Spiral lines loosely coiled. About one and one-half 

 whorls within the operculum can be traced. Area of attachment small, narrow, elongate. 



Mcasurcntcnis of type: Altitude, 11 mm.; diameter, 7^/^ mm. Aperture— altitude, 

 6 mm.; diameter, 3^ mm. 



Type locality: Coosa River, Riddle's Bend, Cherokee County, Alabama. Collected 

 by Herbert H. Smith, October, 1904. 



Type in the Museum of Zoology, University of Michigan. Paratypes in the 

 Alabama Museum of Natural History. 



This species is confined apparently to the Coosa River in Cherokee and 

 Etowah counties, Alabama, above the middle river shoals. Mr. Smith's 

 shells come from only three localities, rather close together. Modesta, to all 

 seeming, is a small local race whose affinities are closest to A. doivniei 

 Lea. It differs from that species in being smaller, having weaker folds, 

 less pronounced plicae, a greater tendency to vary. The bands are not so 

 numerous. The operculum of modesta is much thinner and shows a more 

 decided variability. The impression is given that in the case of this species 

 the operculum has lost much of its usefulness as a protective organ. 



Of 34 specimens from Riddle's Bend i has quite strong folds, 27 are 

 moderately folded suture to base, in 4 the folds can be made out only with 

 a glass and in the case of 2 shells there are no folds. No revolving striae 

 were seen. The plicae consist mostly of flat nodules, irregular, seldom 

 continuous in any one specimen. 



The color varies from a shining yellow to light brown. The banding 

 arrangement is four thin, continuous bands. Only one modification^ other 

 than that in the type, was noted, a single banded specimen lacking the basal 

 band. Many shells have bands in the epidermis which do not show in the 

 aperture. The number of specimens lacking bands exceed those with them. 



The columella is usually porcelain white, sometimes cream-colored, un- 

 iformly regular and rounded. The variation in the peristome is exceedingly 

 slight, this character being usually straight, sometimes a little curved near 

 the suture. 



The operculum is of the picta-formosa-dozvnici type, but is evidently de- 

 generating and varies accordingly in size, form and scupture. Two opercula 

 were observed to have curious little pits upon the anterior side as if 

 diseased. This has not been remarked in the case of any other species. 



Measurements : 



Diameter 



Riddle's Bend, Cherokee County 



Below Minnesota Bend, Cherokee County 

 Fitz's Ferry, Etowah County 



