236 THE CHICAGO ACADEMY OF SCIENCES. 
all of the cusps have well developed cutting-points (Fig. 66).* 
Genttaha: Not examined. 
Distribution: Entire Northern United States, Ontario, 
Canada, and Eastern Mexico. 
Geological distribution: Pleistocene. 
Hatitat: Found plentifully under chips and stones, in rot- 
ting logs, etc., on the edge of forests. 
Remarks: Distinguished from &. armifera by its smaller 
size, triangular aperture, and especially the massive parietal 
tooth which nearly fills up the aperture. The keeled base is 
also a distinguishing feature. From BS. holzingerz it is separated 
by its carinated base, fewer teeth in the aperture and their dif- 
ferent form. It is a very abundant species and of much inter- 
est when studied alive. The shell is carried well upright and 
the motions of the animal are generally slow and methodical. 
Frequently when crawling over a table it will lift up its head 
and a portion of its body until only the tail rests on the sur- 
face. It is very widely distributed, being found in all the 
regions. 
93-' Bifidaria holzingeri Sterki. Text, fig. 67. 
Pupa holzingert STERKI, The Nautilus, Vol. III, p. 37, 1889. 
Pupa holzingeri fordiana STERK1, The Nautilus, Vol. VI, p. 4, 1892.7 
(Variety). 
Shell: Small, cylindrical, turreted, shining, minutely um- 
bilicated; growth lines (striz) minute, oblique; nucleus smooth; 
color whitish, vitreous; whorls five, convex, regularly increas- 
ing, the last two of about equal size and the first three forming 
a rather pointed apex; the last whorl is narrowed and descends 
slightly toward the aperture, and the base is considerably com- 
pressed but not keeled as in contyvacta; just back of the aper- 
ture there is an oblique, elevated ridge formed by a white 
callus, which follows the direction of the growth lines, and ex- 
tends from the suture to the base; behind this ridge the body 
whorl is flattened and impressed by one of the teeth; sutures 
well impressed; aperture lateral, ‘inverted subovate, with a 
slight sinus at the upper part of the outer wall;” six-dentate as 
follows: one on the parietal wall, large, long, high, curved out- 
ward about the center, bifurcated, “the outer branch reaching 
the parietal wall;” one on the columella, high, longitudinal, 
*The descriptions of some of the radulz here enumerated were first given in Journ. Cin. 
Soc., N. H., Vol. XIX, No. 3, pp. 81-89, 1897. 
+ This“is the only reference the writer is able to find concerning this variety. 
yeh Stl ie eae 
