332 



TERRESTRIAL AIR-BREATHING MOLLUSKS. 



Fig. 214. 



In the Southern and Southwestern States from North Carolina to Texas, 

 the species assumes Often, not in all localities, the form de- 

 scribed as bucculenta. I repeat the description and figure's of 

 the typical form, and a small variety from Alabama (Fig. 214). 

 This last often wants the parietal tooth : this form has same 

 jaw, lingual membrane, and genitalia as typical thyroides. 



Shell usually perforate, globose-conic, more or less elevated, 

 rather thin, shining, pale yellowish-green, surface regularly and 

 delicately furrowed by the striae of growth ; whorls 5 or a little 

 more, rounded, and separated by a well-impressed suture ; base 

 convex ; aperture rounded ; peristome forming nearly two 

 thirds of a circle, rather broadly reflected, white, somewhat flesh-colored 

 behind, not completely covering a small umbilical perforation, sometimes en- 

 Fig. 215. 



M. bucculenta. 



M. bucculenta. 



tirely covering it ; parietal wall sometimes bears a small white tooth at the 

 middle, but of tener not. Greater diameter 18^, lesser 15^ mill.; height, 10£ 

 mill. (Vol. HI. PL XI. a.) 



Mesodon clausa, Sat. 



Vol. III. PL IV., central figures. 



Shell subimperforate, conoidly semiglobose, rather solid, with crowded rib- 

 like stria?, yellowish horn-color ; spire subregularly conoid ; whorls 5^, rather 

 convex, gradually increasing, the penultimate subangular, the last rounded, an- 

 teriorly subconstricted and briefly deflected ; umbilicus narrow, almost covered 

 by the reflected peristome ; aperture diagonal, subregularly lunate ; peristome 

 with a heavy, white thickening, uniformly subangularly reflected, its columel- 

 lar portion subdilated. Greater diameter 18|, lesser 16 mill.; height, ll£ 

 milL 



Helix clausa, Say, Journ. Phila. Acad., II. 154 (1821) ; American Conch. <1832), 

 No. 4, PL XXXVII. Fig. 1 ; Binney's ed., 17, PL XXXVII. Fig. 1 ; ed. 

 Chentj, Bibl. Conch., III. 50, PL XIII. Fig. 2. — BinneY, Bost. Journ. Nat. 

 Hist., I. 482, PL XV. (1837); Terr. Moll., II. 107 (excl. syn.), PI. IV. (ex- 

 cepting the outline figures). — DeKay, N. Y.-MolL, 31, PL III. Fig. 13 (1843). 

 — Reeve, Con. Icon., Fig. 694. — Bland, Ann. N. Y. Lye.-, VI. 336. — 

 Pfeiffer, Mon. Hel. Viv., IV. 321. — W. G. Binney, Terr. Moll., IV. 46 ; 

 L. & Fr.-W. Sh., I. 149 (1869). 



Helix Fennsylvanica, Pfeiffer, ex parte, Symt. ad. Hist. Hel., II. 36 ; Mon. 



