HELIX. i21 



aperture widely lunar, somewhat narrowed by a lamelliform tooth on the 

 parietal wall ; peristome acute, reflected, thickened with white callus 

 within ; a transverse internal tubercle on the base of the shell. Greater 

 diam. 11, lesser 10; height G mill. 



Uelix monodon, Rackett, Linn. Trans. XIII, 42, pi. v, f. 2 (1822) ; ed. 



Chenu, 269, pi. xxvii, f. 5. — Wood, Ind. Supplem. pi. vii, f. 15 



(1828); ed. Hasley, 226, f. 15.— Bix.ney, Bost. Journ. Nat. Hist. 



Ill, 360, pi. X, f. 1 (1840) ; Terr. Moll. II, 147, pi. xli, lower figs.— 



Gould, Invertebrata, 174, f. 113 (1841). — Adams, Vermont MoUusca, 



159 (1842).— W. G. BiNNEY, Terr. Moll. IV, 60.— DeKay, N. Y. Moll. 



35, part, excl. syn., pi. iii, f. 19, not f. 21, a, b (1843). — Mrs. Gray, 



Fig. Moll. An. pi. cxciii, f. 11 (ex Bost. Journ., no desc). — Billings, 



Canadian Nat. II, 100, f. 6 (1857).— Morse, Amer. Nat. I, 151, f. 



12, 13 (1867).— Pfeiffer. Mon. Helis. Viv. IV, 320. 

 Helix convexa, Chemnitz, part (excl. syn. et tab. Ixvi, f. 24, 27), pi. x, 



17, 18.— Pfeiffer, Mon. Hel. Viv. Ill, 26S (excl. S et y). — Deshayes 



in Lam. VIII, 112 ; 3d ed. Ill, 308 ; Encycl. Meth. II, 253 (1830) ; 



in Per. /. c. I, 144. — Reeve, Con. Icon. 696 (1852), excl. syn. ; no. 



717 (1854). 

 Helicodonta hirsuta, a, Ferussac, Tabl. Syst. 101, no desc. 

 Stenotrema monodon, Morse, Journ. Portl. Soc. I, 10, f. 13, pi. ii, f. 2 ; 



pi. iv, f. 14 (1864).— Tryon, Am. Journ. Couch. Ill, 56, pi. ix, f. 



18, 20 (1867). 



VAR. FRATERNA. 

 Helix fraterna, Say, Long's Exp. II, 257, pi. xv, f. 3 ; Binney's ed. 30, 



pi. ixxiv, f. 3. — Mrs. Gray, Fig. Moll. An. pi. cxciii, f. 5, no descr. 



— BiNNEY, Bost. Journ. Nat. Hist. Ill, 363, pi. x, f. 2, not of Wood. 

 Helix monodon, DeKay, N. Y. MoU. /. c. ex parte, pi. iii, f. 21, a, b (1843). 



— Wood, Ind. Suppl. pi. vii, f. 15. 

 Helix convexa, Chemnitz, ed. 2, I, iQ, ex parte. — Var., Reeve, Con. Icon. 



/. c.—B, Pfeiffer, Mon. Hel. Viv, I, 420. 

 Helix monodon, B, Pfeiffer, /. c. IV, 320. 



VAR. LEAH. 

 Helix convexa, y, Pfeiffer, /. c. — Var. Chemnitz, I. c. pi. ixvi, f. 24, 25. 

 Helix monodon, y, Pieiffer, IV, 320. — Part Binney, Terr. Moll. pi. xli, 



central figures. 

 Helix hail, Ward, MS. teste Binney. 

 Lister, Syn. Conch, pi. xciii, f. 94. 



All of eastern North America, through Canada. Also in the 

 postpleiocene of the Mississippi Valley. 



The varieties of this shell present remarkable differences in size 

 and coloring, and in the form of the umbilicus. The transverse 

 diameter varies from one-si.xth to three-sixths of an inch, and the 

 form from subglobular in small specimens to a very flattened 



