[ 84 ] * 



covering tlie umbilicus ; base very conves. Yellowisli born 

 color. 



Diam. 16, heigbt 10 mill. 



?c2iyr.Q..:^;'a. Oregon. 



Peculiar in tbis group, for its very close arrangement of 

 sbort bristles all over tbe surface ; tbe old sbells are frequently 

 denuded of tbese, but tben the scars of their insertion are dis- 

 tinctly visible with a glass. As already mentioned, this spe- 

 cies sometimes developes a strong, oblique, parietal tooth, 

 (fig. 12). 



§§ Not hirsute. 

 17 Mesodon Downieana, Bland. 



Flate 8, figure 15. 



Subglobose, thin, subpellucid, with obsolete rib-like stride 

 and crowded minute revolving lines ; spire depressed conical, 

 suture moderately impressed-; whorls 5, convex, the last 

 tumid, scarcely descending, constricted behind the lip ; aper- 

 ture obliquely lunate, lip white, reflected narrowly, nearly 

 covering tbe umbilicus ; base convex. Grreenish horn color, 



Diam. lO'o, height 6 mill. Cc...'..'y, 



University Place, Franklin County, Tennessee. ■ - ■ 

 Like M. Christy i, Bland, in form, but has noi3arietal tooth. 



18« Mesodon clausa, Say. 



Plate 8, figure 16. 



Subglobose, moderately thick, with fine oblique striae ; spire 

 convex, with distinct suture ; whorls 5, convex, the last large, 

 contracted behind the lip ; aperture rounded, lip white, nar- 

 rowly reflected and nearly covering the umbilicus ; base very 

 convex. Light yellowish brown, shining. 



Diam. 13— 15 mill. 'V 



Inhabits all the Western States from the Grreat Lakes to 

 Mississippi and Alabama. 



This species is of the same size as M. Pennsylvaniea and 

 31. 31itcheUiana, inhabiting partially the same region. Its dis- 

 tinctive characters have been already pointed out. It is most 

 abundant in the southwest in a semi-fossil condition. 



