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 (6 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. PL VIII. Fig. N. 



Genitalia unobserved. 



Mesodon devia, GOULD. 



Shell umbilicated, 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 

 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, Pl/LXXIX. 

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



Helix Baskeroillei, 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). 



Helix 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 



