332 



TERRESTRIAL AIR-BREATHING MOLLUSKS. 



Fig. 214. 



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

 tlie species assumes often, not in all localities, the form de- 

 scribed as bucculenta. I repeat the description and fit^ures 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 thyro'ules. 



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

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

 delicately furrowed by the striaj 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. buccitlenta. 



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

 middle, but oftener not. Greater diameter 18|, lesser 15^ mill.; height, 10|^ 

 mill. (Vol. III. PI. XI. a.) 



Mesodon clausa, Say. 



Vol. III. PI. IV., central figures. 



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

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

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

 teriorly subcoustricted 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, 11^ 

 mill. 



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

 No. 4, PI. XXXVll. Fig. 1; BixXNEy's ed., 17, PI. XXXVII. Fig. 1; ed. 

 Chenu, Bibl. Conch., III. 50, PI. XIII. Fig. 2. — Binney, Post. Journ. Nat. 

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

 ceptiug the outline figures). — DeKay, N. Y. MoU., 31, PI. III. Fig. 13 (1843). 

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

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

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



Helix Fennsylvaiiica, Pfeiffer, ex parte, Synib. ad. Hist. Hel., II. 36 ; Mon. 



