102 NEW-YORK FAUNA — MOLLUSCA. 



Anculotus TRIVITTATUS. 



PLATE VII. FIG. 1S7. 



(STATE COLLECTION.) 



Description. Shell elliptical : whorls about five, convex ; suture impressed ; spire short, 

 often eroded, and about the length of the aperture ; inner lip arcuated, with a callus ; aperture 

 oval, rounded beneath, acute above. 



Color. Dark olive, with three dark purple revolving bands on the carina, the central band 

 very narrow. 



Length, 0*5; of aperture, 0*25. 



These species were obtained from Cranesport, in company with the preceding. In some, 

 the bands are obscure or wanting. It appears to be closely allied to A. melanoides of Conrad, 

 but is distinguished by the greater number of its volutions. 



(EXTRA-LIMITAL.) 



A. angulatus. (Conrad, Fr. Wat. Shells, p. 60, pi. 8, fig. 15.) Shells subglobose: body-whorl 

 ventricose, contracted above, biangulated; spire very short; volutions carinated at the suture. 

 Color, olivaceous, with about four series of dark quadrangular spots on the body-whorl. Alabama. 



A. costatus. (Anthony, Bost. Jour. Vol. 3, p. 278, pi. 3, fig. 1. Pl. 7, fig. 139 of this work.) Shell 

 thin, subglobose, with a depressed convex spire: body-whorl ventricose, with about five revolving 

 costae, varying in number, and occasionally obsolete ; whorls four ; sutures conspicuous. When the 

 costae are present, the body-whorl angulated. Color, dark olive in the adult; lighter in the young: 

 columella deep purple at the base. Length, 0-2. Ohio. 



A. dentatus. (Couthouy, Bost. Jour. Vol. 2, p. 185, pl. 4, fig. 7.) Shell rounded or subcorneal, 

 irregular: whorls 5-6, the last large ventricose ; spire obtuse, often eroded, with impressed sutures; 

 aperture rounded, effuse at base. Columella arcuated, with a toothlike process near the base. 

 Color, olive to blackish green, occasionally with 2-3 dark brown transverse bands : columella 

 dark brown or purple. Length, 0*25. Allied to monodontoides. Rapids of Potomac, Virginia. 



A. melanoides. (Conrad, Fr. Wat. pl. 8, fig. 19.) Shell conical, with three volutions: apex eroded; 

 whorls flattened, only rounded at the sutures; lines of growth prominent; body-whorl abruptly 

 rounded; aperture elliptical, about half the length of the shell. Color: epidermis blackish, obscurely 

 banded. Length, 0-5. An Melania? Alabama. 



A. monodontoides. (Id. lb. pl. 8, fig. 16.) Subglobose: body-whorl ventricose, not abruptly rounded 

 above; apex eroded; columella with a large pyramidal tooth at the base ; aperture effuse. Color, 

 horn, with obscure bands. Mr. Couthouy (Bost. Jour. Vol. 2, p. 186) states that the tooth resem- 

 bles a plait, and is on the middle, and not near the base. Virginia. 



A. nigrescens. (Id. Id. pl. 8, fig. 17.) Subconical, truncated at tip: upper whorl hardly convex; 

 body-whorl elongate, contracted above on the labrum; columella flattened, obtusely rounded at the 

 base ; aperture obovate, rather more than half the length of the shell. Color : epidermis blackish ; 

 within dark purple. Maryland. 



