318 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



XLIII. Figs. 1, 2, 3.— BiNNEY, Bost. Journ. Nat. Hist, I. 475, PI. XIII. 

 (1837) ; Terr. Moll., II. 99, I'l. II. — DeKay, N. Y. Moll., 26, PI. II. Fig. 12 

 (1843). — Gould, Invert., 170, Fig. 101(1841); ed. 2, 423 (1870). — Leidy, 

 T. M., I. 252, PI. VI. (1851), anat.— Pfeiffer, Symb., II. 22, exel. 7 and 5 ; 

 Mon. Hel. Viv., I. 290, excl. /3 and 7 ; in Chemnitz, ed. 2, I. 81, PI. XV. 

 Figs. 7, 8 (1847), excl. var. C and D, PI. X. Figs. 4, 5. — Potiez et Miciiauu, 

 Gal. I. 69. —Reeve, Con. Icon., No. 624. — Deshayes in Fer., I. 137, PI. 

 XLIII. Figs. 1, 2, 3, 5. —Billings, Canadian Nat. and Geol., 1857, II. 98, 

 Figs. 2, 3. — Bland, Ann. N. Y. Lye, VI. 358 (1858). — W. G. Binney, Terr. 

 Moll, IV. 43; L. & Fr.-W. Sh., I. 136, Figs. 229, 230 (1869). —Morse, 

 Amer. Nat., I. 6, PI. I. Figs. 1 - 11 ; 96, Fig. 2 (1867). 



Eelixrufa, DkKay ? N. Y. Moll., 44, PI. III. Fig. 30 (1843). 



Mesodon albolabris, Morse, Journ. Portl. Soc, I. 8, Fig. 7, PI. III. Fig. 8 (1864). 



— Tryon, Am. Journ. Conch., III. 39, 44 (1867). 



A species of the Eastern Province. Canada to Arkansas, Georgia to Minne- 

 sota. Also in the Post-pleiocene of the Mississippi Valley. 



Specimens of M. albolabi'is are sometimes found 



FiiT 208 



^^^ J_ bearing a well-developed parietal tooth. Such are 



very plenty in the Alleghany Mountains in Pennsyl- 

 vania. One is here figured (Fig. 208). 



The genitalia and lingual dentition of this form is 

 the same as in the typical form. 



Pfeiffer's var. y and d of the Symbolae are respec- 

 tively major and exoleta. In the Monograph his ^ 

 M. albolabris, var. ^^ perhaps the former, and his y certainly is. In 



Chemnitz ed. nov. he figures exoleta as var. D, and 

 places major as C. In Vol. VII. of the Monographia the synonymy of the 

 group is correctly given. 



Deshayes in Ferussac's History erroneously gives Guadeloupe as the habi- 

 tat. From his reference to Ferussac's plates he seems to confound major with 

 albolabiis. 



Petiver mentions this species in Phil. Trans., 1698, p. 395. 

 I have this species from fourteen States. The series presents very remark- 

 able variation in the height of the spire and in the form of the aperture. From 

 Illinois I have a few of a large variety (greater diameter, 35 mill.), furnished 

 with a strong, tooth-like prominence on the peristome, near its columella extrem- 

 ity. There is a variety, quite common among the Pennsylvania Mountains, 

 characterized by a strong parietal denticle. It might readily be confounded 

 with exoleta, but wants the more ventricose body whorl of the latter, and differs* 

 widely in its genitalia. 



It occurs fossil in the Post-pleiocene. From Natchez Bluff I have speci- 

 mens with a remarkably flattened spire. 

 A reversed individual has been noticed. 

 Animal varying from pure white and cream-color, through various shades of 



