. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 330 TERRESTRIAL AIR-BREATHING MOLLUSKS. bulb, into which the vas deferens enters. The retractor muscle is inserted above the entrance of the vas deferens. Mesodon Wetherbyi, Bland. Shell with umbilicus covered, orbicular-depressed, thin, granulately striate, pale horn-colored ; epidermis dark, covered with oblique, prostrate hairs; spire somewhat conoidal, suture impressed, apex obtuse; whorls 5, Fig. 213. slightly convex, gradually increasing, the last suddenly de- flected, rather gibbous, constricted, beneath convex
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. 330 TERRESTRIAL AIR-BREATHING MOLLUSKS. bulb, into which the vas deferens enters. The retractor muscle is inserted above the entrance of the vas deferens. Mesodon Wetherbyi, Bland. Shell with umbilicus covered, orbicular-depressed, thin, granulately striate, pale horn-colored ; epidermis dark, covered with oblique, prostrate hairs; spire somewhat conoidal, suture impressed, apex obtuse; whorls 5, Fig. 213. slightly convex, gradually increasing, the last suddenly de- flected, rather gibbous, constricted, beneath convex, subangu- late at the periphery; aperture oblique, roundly lunate, with a white, erect, oblique, tongue-shaped parietal tooth; peri- stome thickened, angularly reflected, the upper margin ex- panded, the columellar margin dilated, covering the umbilical perforation. Greater diameter 17, lesser 15 mill.; altitude, 8 mill. M. Wetherbyi. Helix Wetherbyi, Bland, Ann. Lye. Nat. Hist. N. Y., X. 361, 1873. At the base of sandstone cliffs, mouth of Laurel Kiver, Whitley County, Kentucky. Probably a species of the Cumberland Subregion. This species belongs to the same group as dentifera, Binney, and Roemeri, Pfeiffer, but is of smaller size, somewhat more elevated, and readily distin- guished from them by the sculpture and epidermis. It differs from M. divesta, Gould, in having a parietal tooth, and, although in general appearance like a small form of M. appressa^ Say, is without the lamina on the basal margin of the peristome. (Bland.) Jaw as usual in the genus, about 18 ribs. Lingual membrane (PI. VIII. Fig. D) with 35- la erals. It will be seen in the figure that the marginal teeth ha imple, not bifid, inner cutting point, a peculiarity shared by only a few oth r speci Genitalia unobserved. Mesodon thyroi&es, Say. Vol. HI. PI. XL Shell narrowly umbilicated, depressed globose; spire coi pldermis of a uniform yellowish-bro'ivn or russet color; whorls 5, with rallel striae, running
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