Si'BGEXDS PLANORBELLA, Hald. 



Shell with the whirls few ; aperture campanulatc or bell-shaped, 

 prominent. 



Plaiiorliis camiJaiisilatlis, Say. — Sinistral; wliirls longer than 

 wide ; aperture sub-campauulate. 



Inhabits Cayuga Lake. Cabinet of the Academy. 



Shell sinistral, not depressed ; whirls four, slightly striate across ; longer 

 than wide ; spire hardly concave, often plane ; body whirl 

 abruptly dilated near the aperture and not longer behind 

 the dilatation than the penultimate whirl ; suture indented, 

 well defined to the tip, the summits of the volutions being 

 rounded ; aperture dilated ; throat narrow abruptly ; umbili- 

 cus profound, the view extending by a minute foramen to the 

 apex. Greatest length of the body whirl one-fourth of an 

 inch ; breadth from tip of the labrum one-half of an inch ; 

 at right angles to the last, two-fifths of an inch. 



This shell abounds in some of the small streams which dis- 

 charge into Cayuga Lake, where it was collected by Mr. 

 Jessup, who presented specimens to the Academy and to me. It is readily 

 distinguished from other species, by the sudden dilatation of the outer 

 whirl, near the aperture in the adult shell, forming a large oval chamber. 

 The summit of the outer whirl, behind the dilated portion, is not, or 

 hardly elevated above the summits of the other volutions. (^Say.) 



Planorbis carnpanulatus, Sat, Jour. Acad. Nat. Sc. II, 166 (1821) : Bin- 

 key's ed. p. 64. — Haldeman, Mon. 9, pi. i, f. 7-11 (1844). — Gould, 

 Invert. 204, f. 133 (1841).— Adams, Shells of Vt. 155 (1841).— De- 

 Kay, N. Y. Moll. 61, pi. V, f. 99* a, h (1843).— Kuster in Chemx. ed. 

 2, p. 52, pi. ix, f. 7-10.— Axon. Can. Nat. II, 204, fig. (1857). 



Planorbis hellus, Lea, Tr. Am. Phil. Soc. IX, 6 (1844) ; Proc. II, 32 (1841). 



Planorbis bicarinatus, Sowekby, Gen. pi. iv. 



Plunorbella campanulata, Chenu, Man. de Conch. II, p. 482, f. 3559. 



Helix angnlata,'SiiEPP\RD, teste J. de C. SowEKBY,*Fauna Boreali- Ameri- 

 cana, III, 315. 



It ranges from New England through the northern tier of 

 States to Minnesota. 



