316 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



hardly have been expected, so utterly different are they from those of albolabris. 

 Again, Ave should hardly have expected to find such a difference in the same 

 genus as the presence and absence of side cutting points on the central and 

 first lateral teeth. 



Mesodon major, Binney. 



Vol. III. PI. I. 



Shell imperforate, conoidly subglobose, solid, with crowded, fold-like striae, 

 and a few interstitial microscopic revolving lines ; reddish horn-color or chest- 

 nut ; spire conoid, the apical point small ; whorls G, convex, the last ventricose, 

 scarcely descending in front ; aperture diagonal, roundly lunate, whitish with- 

 in ; peristome with a white thickening, its terminations joined by a thin callus, 

 the right and basal portions rather broadly expanding and reflected, the colu- 

 mellar portion subdentate, dilated, subexcavated, adhering. Greater diameter 

 37|, lesser 31 mill.; height, 26 mill. 



Helix major, BlNNET, Bost. Journ. Nat. Hist., I. 473, PI. XII. (1837); Terr. 

 Moll., II. 96, PI. I. — DeKay, N. Y. Moll., 45 (1843). —Mrs. Gray, Fig. of 

 Moll. An., PI. CCXCI. Fig. 1, from Bost. Journ., no descr. — W. G. Binney, 

 Terr. Moll., IV. 43; L. & Fr.-W. Sh., I. 135 (1869). — Pfeiffer, Mon. Hel. 

 Viv., IV. 320. 



Helix albolabris, var., Ferussac, Hist., PI. XLIII. Fig. 4; PI. XLVI. a, Fig. 7. 

 — Deshayes in Fer., part. — Pfeiffer, Symbohe, II. 22; Mon. Hel. Viv., 

 I. 290; in Chemnitz, ed. 2, I. 81. — Reeve, Con. Icon., 656. — Bland, N. 

 Y. Lye., VI. 359. 



Mesodon major, Tryon, Amer. Journ. Coneh., III. 43 (1867). 



This form seems to inhabit a narrow strip of territory east of the mountains 

 from Abbeville, South Carolina, to the Gulf of Mexico. At Aiken, South Car- 

 olina, it is well marked, more so at Macon, Columbus, and Butler, Georgia. 

 Dr. Binney found it in West Florida. It is common in the City Cemetery of 

 Macon, Georgia. 



It is much more globose than albolabris, of a coarser and more solid texture, 

 and the stria? of increase are much more raised and prominent, so much so, 

 indeed, as to leave distinct grooves between them. The revolving stria?, so 

 distinct on that shell, are either wanting or very indistinct. The aperture is 

 smaller in proportion to the size of the shell, less flattened towards the plane of 

 the base, and more rounded. The parietal wall and umbilicus are in many in- 

 stances covered with a smooth and shining, semi-transparent, testaceous callus, 

 and in one specimen in my cabinet bears a well-developed tooth. The margin 

 of the peristome is thickened, the peristome itself is narrower, less abruptly 

 reflected, and not so much flattened, and there is often a tooth-like process on 

 the inner and upper side of the margin near the umbilicus. The color of the. 

 epidermis is generally much darker. The only considerable variation in the 

 characters of the shell is caused by the depression of the spire in some individ- 



