390 A MANUAL OF AMERICAN LAND SHELLS. 



througbout, ending in a stout, oval bulb, into which the vas deferens 



enters. The retractor muscle is inserted above the entrance of the vas 



deferens. 



Mesodoti divestiis, Gould. 



Shell imperforate, depressed, somewhat discoidal, of medium thick- 

 ness and a dingy horucolor, sculptured with coarse, oblique furrows; 

 Fig. 424. spire slightly convex; whorls about 6, a little convex, and 

 separated b}^ a well-imin'essed suture ; the outer whorl is 

 a little augular at its periphery; beneath it is more 

 smooth, moderately convex, with the central region exca- 

 h vated and covered with a glazing of white callus; the 

 aperture is lunate and very oblique; the peristome is 

 white, broadly reflected, its basal portion horizontal and 

 its outer portion flexuous. Greater diameter 20, lesser 15""»; height, 



Oram 



Eeiix dcjeda, GouLD, Terr. Moll., ii, dl. Not preocc. in Mesodon. 



Helix abjecla, Gould, Proc. Bo-st. Soc. Nat Hist., iii, 40 (Oct., 1848) ; Terr. Moll., ii, 



122, pi. xii, a, fig. 2. — Pfeiffer. Mon. Hel. Viv., iii, 270. 

 Helix divesia, Gould, Terr. Moll., ii, 357.— W. G. Binxey, Terr. Moll., iv, 51 ; L. & 



Fr.-W. Sh., i, 13f (18(i9).— Pfeiffer. Mon. Hel. Viv., iv, 322. 

 Mesodon divesia, Tryon, Am. Journ. Concb., iii, 45 (1867). — W. G. BIXXEY, Terr. 



Moll., V, 329. 



Washita Springs, Arkansas; Vernon County, Mississippi. It may 

 prove to be a species of the Texan Subregion. 



Jaw with 10 ribs. 



Lingual membrane (Terr. Moll., Y, Plate XYI, Fig. V) as in albo- 

 lahris ; teeth 4G-1-4G, with IG laterals. 



The genitalia are as usual in the genus; the penis sac is very long, 

 cylindrical, stout, tapering at the top; the vas deferens enters at its 

 apex; the retractor muscle is attached to the vas deferens; the genital 

 bladder is short, oval, stout, on a short, stout duct. 



Mesodon jejiiiiiis, Say. 

 Shell umbilicated, subglobose ; epidermis corneous, nearly smooth ; 

 Fig. 425. spire rather prominent ; suture impressed ; whorls rather more 

 C|^^ than 5, the last ample; stride of increase hardly visible; peri- 

 M.jejunus. stomc whitc, vcry narrow, reflected, a deep groove behind it; 

 aperture well rounded, semicircular, considerably contracted by the im- 

 pressed groove behind the peristome and a corresponding testaceous 

 di'i)osit or rib within; umbilicus small, round, not expanded; umbili- 

 cal region not imi^ressed ; base convex. Greater diameter 8, lesser 7™™; 

 height, d^"""^. 



