230 



THE CHICAGO ACADEMY OF SCIENCES. 



Shell: Cylindrical, shining, smooth; surface covered with 

 fine, oblique growth lines, the apex being smooth; color whitish; 

 whorls five to six, convex, the apical obtuse, regularly increas- 

 ing in size; sutures well impressed; aperture subcircular, wide, 

 two-thirds as high as the width of the last whorl ; there are one or 

 two small, white, pointed teeth on the parietal wall (sometimes 

 altogether wanting), and the columella is provided with a small 

 swelling or tuberosity; peristome reflected, white, terminations 

 separated and joined by a thin callus; umbilicus narrowly per- 

 forated (Fig. 61). 



Fig 61. 



BIFIDARIA CORTICARIA Say, showing variations of teeth. (Binney, 

 Fig. 356.) 



Length, 2.25; diameter, 1.00; aperture long, 0.75 mill. (10240.) 

 Animal: Of the usual form; color generally whitish, of a 

 trifle darker color on the eye-peduncles and head. The foot is 

 of unusual length. 



Jaw: Considerably arched and tapering to a blunt point 

 at either end; concave margin bearing a rounded median pro- 

 jection of considerable size. The anterior surface is longitudi- 

 nally striated (Fig. 62). 



Fig. 62. 

 Jaw of BIFIDARIA CORTICARIA Say. (Original.) 



Radula: Asusual; formula ^ T +|+^+|+^ T (12- I- 12); 

 three perfect laterals. 



Genitalia : Unknown. 



Distribution: "Ontario and Maine to Minnesota, south to 

 South Carolina and Mississippi." (Pilsbry.) 



