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 onthe eye-peduncles and head. The foot is 
of unusual length. 
Faw. 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 38-+4+}1-+4+,8, (12—I—12); 
three perfect laterals. 
Genttaha: Unknown. 
Distribution: “Ontario and Maine to Minnesota, south to 
South Carolina and Mississippi.” (Pilsbry.) 
