MESODON. 337 



timate whorl is sharp, not reflected nor thickened, but elsewhere reflected, 

 thickened by a whitish callus within, the edge of which forms a distinct portion 

 of the peristome, and has an obsolete tooth-like development near the columella. 

 The aperture is more lunate than in jejuna. 



M. Mobiliana may be compared, so far as regards the tumid base, small um- 

 bilicus, constricted aperture, and gibbous character of the superior part of the 

 last whorl behind the aperture, with a Texan form in my cabinet of Dorcasia 

 Berlandieriana. 



The measurements of my largest specimen (G whorls) of M. Mobiliana, from 

 Baldwin, are as follows: Greater diameter 10, lesser 7 mill.; height, 6 

 mill. 



Jaw as usual; 10 ribs. 



Lingual membrane of the true species, from Baldwin County, Alabama, has 

 25 — 1 — 25 teeth, with 10 perfect laterals. There, are decided side cusps and 

 cutting points to centrals and laterals ; the transition to the marginals is made 

 as usual, the inner cutting point becoming bifid. PI. VIII. Fig. N. 



Genitalia unobserved. 



Mesodon devia, Gould. 



Shell umbilieated, solid, depressed-globose, pale yellowish horn-color, or 

 brown, with fine lines of growth ; whorls 6, convex, suture well defined ; be- 

 neath slightly convex, and perforated by a moderate-sized umbilicus, which 

 appears to have an obtuse channel revolving on the 

 whorls within it ; periphery rounded ; aperture trans- Fig. 220. 



verse, obliquely lunate ; peristome thickened, white, or 

 sometimes rufous, rather broadly reflected, horizontal at 

 base, the upper edge sometimes bearing a tooth-like pro- 

 cess, the inner edge dilated into an elongated, lamellar, 

 white, tooth-like process, and abruptly turning up to M. devia. 



form a short columella, where it dilates, and partly sur- 

 rounds the umbilicus ; near the upper margin, and on the parietal wall, 

 is a white trigonal tooth. Greater diameter 24, lesser 19 mill.; height, 

 14 mill. 



Helix devia, Gould, Proc. Bost. Soc. Nat. Hist., II. 165 (1846) ; Terr. Moll., 

 III. 11 ; Moll, of Expl. Exped., 69, Fig. 74, Addenda, "501 (1852). — Pfeiffer, 

 Mon. Hel. Viv., I. 383. — W. G. Binney, Terr. Moll., IV. 17, PI. LXXIX. 

 Fig. 13 ; L. & Fr.-W. Sh., I. 152 (1869). 



Helix Baskervillei, Pfeiffer, Proc. Zool. Soc., 1849 ; Mon. Hel. Viv., III. 230, 

 in V. referred to devia. — Reeve, Con. Icon., Fig. 684. 



Mesodon devia, Tryon, Am. Journ. Conch., III. 42 (1867). 



Hellv Mullani, Bland and Cooper, Ann. N. Y. Lye, VII. 363, PI. IV. Figs. 

 16, 17 (1861).— W. G. Binney, L. & Fr.-W. Sh., I. 130 (1869). 



Triodopsis Mullani, Tryon, Am. Journ. Conch., III. 52 (1867). 



vol. iv. 22 



