THE NAUTILUS. 



9 



just behind the apex, apex snbcentral, only slightly behind the 

 centre, obliquely elevated, acute, spine-like, somewhat turned 

 toward the right side, finely radially striate, apical depression 

 small, oval and situated on the left side of the tip of the apex; 

 pale green with the apical region deeply tinged with rose color; 

 anterior slope very slightly convex; posterior slope oblique and 

 nearly rectilinear below the base of the apex; lateral slopes 

 slightly convex and about equally oblique; growth lines regular, 

 fine and distinct, the apical striae extend down over the upper 

 part of the shell giving a shagreened appearance to the surface 

 as they intersect the growth lines, but become mere ripples 

 toward the margin. 



Length 5.25, width 4, alt. 1.25 mm. 



Types, (No. 20371 Coll. Walker), from the Coosa River at 

 Wiliiamsville, Shelby Co., Ala., collected by A. A. Hinkley. 

 Cotypes in the collection of Mr. Hinkley. Also from the Coosa 

 River above Wetumpka ^Hinkley) and at Leota Shoals; Fort 

 William Shoals; Shoal two miles above Coosa Valley; Vincent 

 Shoal two miles above Upper Clear Creek and Peckerwood 

 Shoals (H. H. Smith). 



All of the Smith shells were found on or under stones, which 

 is apparently the usual habitat of the species, differing in this 

 respect from filosa, which is almost invariably found on living 

 Plev roceridcB. 



I have adopted for this species the very appropriate name 

 suggested by Dr. Pilsbry soon after its discovery. 



The peculiar depressed shell of rhodacme with its spine-like 

 apex and characteristic radula differentiate it very sharply from 

 the species included under Rhodacmea s. s. and justifies the 

 establishment of a special section for it and similar species. 



Rhodacmea gwatkiniaxa, n. Bp. PI. I, figs. 3, 7 and 9. 



Shell rather small, depressed conic, oval; apex nearly cen- 

 tral, somewhat turned to the right, acute and spine-like, finely 

 radially striate; apple-green with the apex tinted with old-rose 

 color; anterior slope slightly convex; posterior slope oblique 

 and nearly straight below the projecting apex; lateral slopes 

 straight below the base of the apex and equally oblique; growth 



