84 



LAND AND FRESH-WATER SHELLS OF N. A. [PART L 



150. 



Helix labyrinthica, Say. — Shell umbilicated, globose-couic, 

 brownish liorn-uolor, with stout ribs above, and below lighter with arbo- 

 rescent wrinkles ; spire obtuse ; umbilicus narrow, pervious ; aperture 

 scarcely oblique, lunately rounded ; peristome briefly re- 

 flected, thickened ; parietal wall with three revolving, deeply 

 entering, parallel laminre, the central further within the 

 aperture and less developed, and around the axis one stout 

 lamella-like rib not reaching the columella ; on the base 

 of the outer whirl are two short, deeply seated internal re- 

 volving rib-like laminae. Greater diam. 2J, height If mill. 



Helix lahyrinthica, Say, Journ. Phila. Acad. 1, 124 (1817) ; 

 Nich. Encycl. ed. 3, IV (1819) ; ed. Bixxey, 10.— Binsey, 

 Bost. Journ. Nat. Hist. Ill, 393, pi. xxvi, f. 1 (1837) ; Terr. Moll. 



11, 202, pi. xvii, f. 3.— Gould, Invertebrata, 184, f. lOG (1841).— 

 Adams, Vermont MoUusca, 160 (1842). — Ferussac, Tab. Syst. 38; 

 Hist. pi. li, B, f. 1.— Pfeiffer, Symbolse, II, 31 ; Mon. Hel. Viv. I, 

 416.— Chemnitz, 2d ed. I, 382, t. Ixvi, f. 17-20.— Reeve, Con. Icon, 

 no. 728 (1852).— DeKay, N. Y. Moll. 39, pi. iii, f. 31 (1842).— 

 Deshayes in Per. I, 210.— W. G. Bixxey, Terr. Moll. IV, 95.— 

 Morse, Amer. Nat. I, 545, f. 41, 42 (1867). 



Strohila labyrinihica, Morse, Journ. Portl. Soc. I, 26, f. 64-67, pi. ii, f. 



12, a b ; pi. viii, f. 68 (1864).— Tkyox, Am. Journ. Conch. II, 259, 

 pi. iv, f. 44 (1866). 



Inhabits all of eastern North America.' Also occurs in the 

 postpleiocene of the Mississippi Yalley. 



Mr. Morse has lately given the following description of the 

 internal lamina which characterize this species : — 



The shell has been described as having one revolving tooth within the 

 aperture, and sometimes a second one ter- 

 minating farther within the aperture. I 

 have always found this second one con- 

 stant, and also a third one but slightly 

 raised between these two. At the base of 

 the shell and far within the aperture are 

 two more revolving ribs, running about a 

 third of one volution. These are plainly 

 visible through the substance of the shell. 

 A heavy columellar tooth or rib extends 



Eeluc lahyrinthica, enlarged. ^^^^ ^ ^^.^^^ ^.^^^^^^ ^.^^^.^ ^j^^ aperture, 



Bearly one volution back. This columellar tooth thickens the substance 



Fig. 151. 



' Woodward (Man. 384) refers an extinct English Eocene IleUx to this 

 species. I have seen no specimens of it, but cannot believe it identical. 

 Mr. Bland writes m6 that he has received from France a fossil shell under 

 the name of //. labgrinthicula, apparently identical with our species. 



