118 . A MANUAL OP AMERICAN LAND SHELLS. 



■with a short, stout duct, but ia germanum (Fig. M) it is globular, aud 

 has a long, narrow duct. It must, however, be borne in mind that 

 in my anatomical studies of our species I bave had such wealth of mat- 

 ter to examine I have not compared many individuals of any one 

 species to ascertain how constant the characters are. 



In both species the retractor muscle of the penis is attached to the 

 vas deferens a short distance before the latter organ enters the penis 

 sac, which it- does at the apex of the last. 



Jaw : see above. 



Liugual membrane (Terr. Moll., V, Plate YIII, Fig. P) with 33-1-^3 

 teeth, 15 laterals, the sixteenth tooth having a bifid cutting point. 

 There are decided side cusps and cutting points to the central and 

 lateral teeth. 



Mesodon devius, Gould. 



Shell umbilicated, solid, depressed- globose, pale-yellowish horn- 

 color or brown, with fine lines of growth ; whorls (J, convex, suture 

 well defined ; beneath slightly convex, and perforated by a moderate- 

 sized umbilicus, which appears to have an obtuse channel revolving 

 Fir.. 85. on the whorls within it ; periphery rounded ; aperture 



transverse, obliquely lunate ; peristome thickened, 

 white, or sometimes rufous, rather broadly reflected, 

 horizontal at base, the upper edge sometimes bearing 

 M. devius. a tooth-like process, 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 surrounds 

 the umbilicus ; near the upper margin, and on the parietal wall, is a 

 white trigonal tooth. Greater diameter 24, lesser 19""' ; height, 14™™. 



Helix decia, Gould, Proc. Bost. Soc. Nat. Hist., ii, 1G5 (184G); Terr. Moll., iii, 11; 



Moll, of Expl. ExpecL, 69, fig. 74, addeuda, *501 (1852).— Pfeiffkr, Mou. 



Hel. Viv., i, .383.— W. G. Binney, Terr. Moll., iv, 17, pi. Ixxix, fig. 13; 



L. & Fr.-W. Sh., i, 1.^j2 (1869). 

 Helix Baskei-villei, Fffafvkr, Proc. Zool. Soc, 1849 ; Mon. Hel. Viv., iii, 230, in v 



referred to deiia. — Reeve, Con. Icon., fig. 684. 

 Mesodon devia, Titvox, Am. Jour. Conch., iii, 42 (1867). — W. G. Binney, Terr. Moll., 



V, 337. 

 Helix MuUani, BhASD and Cooper, Ann. N. Y. Lye, vii, 363, pi. iv, figs. 16, 17 



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

 Triodoima Mullani, Tryon, Am. Jour. Courb., iii, 52 (1867). 

 Triodopnis Hatfordiana W. G. Binney, Terr. Moll., v. 309, fig. only, not description, 



not of J. G. Cooper. 



