ANCULOSA. 



391 



and develops a fold on the columella. In this state it be- 

 comes dentata, Couthuoy, or mo7iodontoides, Conrad ; while 

 in parts of the Potomac and Susquehanna it becomes large, 

 heavy and inflated. 



I have selected a number of figures to show the transition 

 from one form to another. The shells Fig. 748. Fig. 747. Fig. 749. 

 represented by figures 747, 7-48, 749 

 (collected by me, cohabiting with the 

 typical species at Harper's Ferry, 

 Virginia, and at Washington, D.C.), 

 merge into IMr. Lea's A. carinata and varia?jilis. The descrip- 

 tions of these species here follow accompanied by illustrations 

 of the tj-pes. 



Anculosa carinata. — Shell ovately couical, carinate, dark olive; spire 

 rather short; sutures small; whorls six; aperture small, round, with- 

 Fig. 750. Fig. 751. ia whitish, sulcate ; columella rather thick, purple. 

 Habitat. — Roanoke River, Lafayette, Virginia. 

 Diameter, -38; length, -52 of an inch. 

 Observations. — A single specimen only of this 

 interesthig species was sent to me by Dr. Warder. 

 It has some resemblance to Anculosa dissimilis, Sa}\ It differs in 

 having a smaller and rounder aperture and in having p.;,, ~^r, yis 753, 

 three carinas, the middle one being the largest. The ap- 

 erture is rather more than one-third the length of the 

 shell. The cariuae are acute. — Lea. 



Anculosa variabilis. — Shell obtusely conical, thick, either banded 

 or horn-colored, carinate or smooth; sutures linear; whorls six, flat- 

 Fig. 754. Fig. 755. tcued ; aperture large, nearly round ; colu- 

 mella thick white or purple. 



Habitat. — Roanoke River, Lafayette, and 

 near Shenandoah Spring Brook. 



Observations. — Three .'specimens are before 

 me, all of which differ more or less. Two of Fig. 75s. Fig. 757. Fig. 756. 

 them are rather acutely carinate, witii a da;k 

 epidermis and three rather large bands, the 

 other is of a rather light horn-color witli indis- Wij^] 

 tinct bands in the interior, and having no carina 

 on the lower whorl. On the columella there is a sliglit swelling. 

 The aperture is about one-half the length of the shell. — Lea. 



