THE NATURAL HISTORY SURVEY. PES) 
peristome with the upper margin; this tooth extends downward — 
into the throat of the aperture; a second tooth, thick, rounded 
and massive, is situated far within the aperture, just where the 
throat turns into the body whorl and also where the umbilicus 
is placed; two teeth are placed on the peristome, one near the 
base and one on the right side; both are conical and tooth-like 
and are directed toward the center of the aperture; two other 
teeth are frequently developed, one conical but small near the 
junction of the peristome and body-whorl, and one rounded 
and massive situated on the base near the larger one before 
mentioned; peristome thin, terminations approaching, broadly 
reflected and connected bya thin callus; base of shell com- 
pressed to form a keel, which extends from the edge of the 
aperture to the umbilicus; umbilical region indented, opening 
small (Fig. 64). 
BIFIDARIA ARMIFERA Say, showing variations. (After Binney, Fig. 353.) 
Length, 4.00; width, 2.25; aperture length, 1.60; width, 1.25 mill. (10288.) 
« 450; « 295:  « «“ 160; “ 125 “ (10288) 
Animal: Of the usual form; color whitish on foot; head, 
neck, and eye-peduncles black. The eye-peduncles are very 
long and tapering, and the whole animal is large and graceful. 
The foot measures 2 mill. in length and 1 mill in width, and is 
sometimes spotted with white. 
Faw: Not examined. 
Radula formula: 37;+4+4+4+32; (1I4—1—14); teeth of 
the usual form; the central tooth is small, long and narrow, 
with a small tricuspid reflection; lateral teeth rather wide and 
bicuspid; marginal teeth as in the other members of the genus. 
Genitalia: Unknown. 
Distribution: Provinces of Ontario and Quebec, Canada, 
United States from Atlantic to Pacific. 
