Anculosae of thk Alabama River Drainage 41 



remarking superficial resemblances to plicata which later he would probably 

 have considered unimportant. 



The peculiar plicae for which Conrad named his species does not occur 

 in all shells. Nor do all the shells have tubercles or beads or sculpture 

 of that nature. The folds upon which the nodules are formed vary in num- 

 ber from one at the suture to several which continue to the base. On one 

 lot from the Forks of the Black Warrior, 19 had each one fold, 5 had two or 

 more. 18 were smooth. Of 94 from Tuscaloosa, 8 only were smooth. Ma- 

 terial from shoals near Lock 15 consisted of 66 shells with from one to four 

 folds, 5 with folds to the base, 19 that were smooth. The tubercules and 

 plicae of the Tombigbee River shells were rather- obscure. Fine growth 

 lines parallel with the peristome are common to all the shells, vaiying slight- 

 ly in strength. Faint revolving lines crossing the growth lines are to be 

 found with a strong glass. 



Eight banding arrangements were noted in plicata from the Forks of the 

 l)lack Warrior, the number of banded individuals being only slightly in ex- 

 cess of those without such ornamentation. The most common arrangement 

 was four thin equidistant lines of coloring matter, the two next most common 

 having respectively a line at top and base and a line at suture, periphery 

 and base. In the Jefferson County shells, the arrangement of three bands 

 was the prevailing form and this was so also in the instances of plicata 

 from Tuscaloosa and Lock 15. Frequently bands appear on the epidermis 

 while absent in the shell material of the aperture. 



The columella of plicata is smooth, rounded and usually the upper half 

 is splashed with brown. It has never the gross, buttressed effect which 

 occurs in some of the larger Anculosae of the Coosa River. The aperture 

 is bluish-white as a rule, though sometimes pink or. pure white. The peri- 

 stome is sharp-edged, firm, very slightly curved. Conrad described his shell 

 as "greenish or blackish." Uncleaned shells are covered with a black deposit 

 of mineral matter. Green shells do occur, but brown is the most frequent 

 color. 



Even among the juvenile shells individuals with uneroded spires are ex- 

 tremely rare. The nuclear whorls of a specimen from near Lock 15 are 

 smooth, elevated, without sculpture. No line between these whorls and those 

 which follow is indicated. An uneroded adult specimen of plicata would 

 probably have seven or eight whorls. Of 32 juvenile shells from the Forks 

 of the Black Warrior, seven are as strongly carinate as the young of praerosa 

 Say and serve to make plainer the relationship of plicata with aiiipla. The 

 other juveniles are rounded or subangulated at the periphery. 



The operculum is dark red, of moderate thickness, sometimes wider just 

 below the rounded apex than af the base. Left margin curved, right margin 

 slightly more so, inclined to tear. Growth lines light to coarse, occasion- 

 ally fanlike as in opercula among Goniobasis. A few opercula have a wavy 

 sculpture near the outer edge parallel with the right margin. The whorls are 

 three, the first two being more sharply defined than in ampla. They are 

 closely coiled. 



