THE NATURAL HISTORY SURVEY. 233 



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 by a 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). 



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. (10238.) 

 4.50; " 2.25; " " 1.60; " 1.25 " (10238.) 



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 i mill in width, and is 

 sometimes spotted with white. 



yaw: Not examined. 



Radula formula: ^! T +|+^+^+^l T (14 I 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. 



