OF CONCHOLOGY. 221 



dianu'tcr. Possibly in some of the most marked instances these 

 differences might be regarded as specific. From all I can learn, 

 I infer some of the varieties of A. prcerosa occupy isolated sta- 

 tions, not being mingled together indiscriminately. This infer- 

 ence seems to be confirmed by the occurrence of a very well 

 ■characterized variety at a point on the Tennessee River from 

 whicli Mr. Wheatley has numerous specimens. 



71. Ancidosa siibglobosa, Say. This species is somewhat ra.re in 

 the HoLston, but occurs in considerable numbers in Little River. 

 The young are smooth, shining, depressed, subglobose, with a 

 somewliat pointed, elevated apex. The outer lip differs con- 

 stantly from that of Cincinnatiensis (= tintinnabulum, Lea). 

 The young shells also very decidedly differ from those of Ancu- 

 losa (Mel.) virgata, Lea, which Mr, Tryon has placed in the 

 synonymy of suhglohosa. 



12. Ancidosa Tryo7ii, Lewis. Plate , fig. . Shell pear- 

 shaped, with the apex somewhat broadly and regularly rounded; 

 wider and subconstricted below ; suture slightly impressed on 

 the apicial whorls, more conspicuously impressed below ; apex, 

 in very young shells, a minute, elevated, dark point, which at 

 later stages of growth is lost by erosion, usually leaving a mi- 

 nute axial pit ; whorls 3 (to 4 ?)* rapidly enlarging ; aperture 

 outwardly somewhat regularly rounded from the slight constric- 

 tion below the suture to the base — acutely angular above, suban- 

 gular below ; outer lip sharp, thicker within ; pillar much thick- 

 ened, having a subtubercular calcareous deposit near the supe- 

 rior angle of the aperture ; plane of the aperture nearly regular, 

 and obliquely inclined to tiie axis. Color variable — yellow, 

 orange, olivaceous, purple or brownish. Bands many, two or 

 none; sometimes visible within when obsolete without. Length 

 0*90 inch. Width 0-60 inch. Aperture nearly |- the length of 

 the yhell. 



In Conch. Jour. vol. ii, page 133, figures 101. 102, Mr. Tryon 

 presents varieties of this species, as Anculosa tceniata, Con. 

 A. tamiata is, perhaps, a smaller species than A. Tryoni^ less va- 

 ried in form, color and bands, and also exhibits peculiarities in the 

 arrangement and modification of the bands not observable in A. 

 Tryoni. The suture and also the form of the whorls are differ- 

 ent. Occasional specimens of A. tceniata are somewhat disposed 

 to exhibit broad, slightly elevated, revolving lines on their sur- 

 faces. This feature is absent in A. Tryoni, which may be char- 

 racterized as a smooth species. A. tceniata also belongs to a dif- 

 ferent system of drainage, viz., the Alabama River and its trib- 



* The apex of the adult specimeos is usually cansiderably eroded. 



