324 TERRESTRIAL AIR-BREATHING MOLLUSKS. 



Mesodon elevata, SAY. 

 Vol. III. PI. IX. 



Shell imperforate, very convex, elevated, almost conical ; epidermis yellow- 

 ish horn-color ; whorls nearly 7, rounded, with fine, oblique, transverse striae, 

 the last ventricose ; suture distinct ; aperture contracted by the peristome, 

 somewhat triangular ; peristome white, thickened, reflected, its basal portion 

 with an obsolete, lamellar denticle ; parietal wall with a large, white, robust, 

 obliquely curved tooth ; umbilicus covered. Greater diameter 25, lesser 20 

 mill. ; height, 7 mill. 



Helix elevata, SAY, Journ. Acad. Phila., II. 154 (1821) ; American Conchology, 

 No. 4, PI. XXXVII. Fig. 2 (1832) ; BINNEY'S ed. 27, PL XXXVII. Fig. 2 ; 

 ed. CHENU, Bibl. Conch., III. 48, PL XIII. Fig. 2, a. BINNEY, Bost. Journ. 

 Nat. Hist., I. 490, PL XIX. (1837); Terr. Moll., II. 126, PL IV. LEIDY, 

 T. M. U. S., I. 256, PL X. Figs. 4, 5 (1851), anat. DEKAY, N. Y. Moll., 36, 

 PL III. Fig. 20 (1843). MRS. GRAY, Fig. Moll. An., PL CXCI. Fig. 7, no 

 descr. PFEIFFER, Symb. Hist. HeL, II. 27; Mon. Hel. Viv., I. 317; in 

 CHEMNITZ, ed. 2, I. 56, PL VII. Figs. 11, 12 (1846). REEVE, Con. Icon., 

 No. 681 (1852). DESHAYES in FER., I. 329. 



Helix Tenncssecnsis, LEA, Trans. Am. Phil. Soc., IX. 1 ; Obs., IV. 1 (1844) ; 

 Proc., II. 31 (1841) ; TROSCHEL'S Arch. f. Nat, 1837, II. 124. 



Helix Knoxvilliana, FERUSSAC, Hist., PL XLIX. Figs. 5, 6. 



Xolotrema elevata, TRYON, Am. Journ. Conch., III. 48 (1867). 



A Post-pleiocene species, now found in the Interior Region from Georgia 

 (on the banks of the Tennessee River) to Wisconsin ; from New York to 

 Missouri ; not east of the Alleghanies. 



Animal : ashy brown on the upper surface, lighter on the posterior extremity 

 and sides ; mantle grayish-white ; glands prominent and distinct. (See Bost. 

 Journ. Nat. Hist., I. PI. VIII.) 



There is a form furnished with a brownish, revolving band upon the body- 

 whorl ; found ia Eastern Tennessee. 



Jaw as usual in the genus ; over 12 ribs. 



Lingual membrane (PL VIII. Fig. M), with about 45145 teeth, 17 lat- 

 erals ; the eighteenth tooth having its inner cutting point bifid. 



Genitalia (see Vol. I., J> f c.). Penis sac long, stout, cylindrical, receiving re- 

 tractor muscle and vas deferens at its summit ; genital bladder long, rounded, 

 stout, gradually and obtusely attenuated above, with a short duct. 



Mesodon Clarki, LEA. 



Shell imperforate, globosely rounded, regularly and finely striated, reddish 

 horn-color ; spire obtusely conic ; whorls 7, convex, Avith delicate incremental 

 striae, the last one very globose and rounded below ; aperture lunate ; peris- 

 tome white, thickened, reflected, its basal termination quite heavy and cover- 



