234 THE CHICAGO ACADEMY OF SCIENCES. 
Geological distribution: Pleistocene; Loess. 
Habitat: Yound in stations similar to the other Pupide. 
Remarks: Armifera is one of our most characteristic spe- 
cies, distinguished by its cylindrical, swollen shell and large 
denticles in the aperture. It is the largest species of the genus 
(in this region) and is very common, being found in little colo- 
nies. Its habits resemble those of contracta. The animal is 
very slow and deliberate in movement and does not readily 
crawl about. It is found in the southern and western regions. 
92. Bifidaria contracta Say, pl. xxx, fig. 8. 
Puparontracta SAY, Journ. Phil. Acad., Vol. II, p. 374, 1822. 
Pupa deltostoma CHARPENTIER in CHEMNITZ, ed. 2, p. 181, pl. xxi, figs. 
17-19. 
Shell: Subconical, smooth, shining; growth lines very 
fine, oblique, apex smooth; color whitish; whorls five to six, 
Fig. 65. 
BIFIDARIA CONTRACTA Say. (Binney, Fig. 35334.) 
convex, forming a pretty regular cone from the last whorl to 
the apex; the last whorl is a little ventricose, and is impressed 
behind the reflected peristome; apex obtuse; sutures deeply 
impressed; aperture somewhat triangular, narrow and long, 
expanded at the peristome and diminishing in size toward the 
throat, four-dentate, as follows: one large, entering tooth on 
the parietal wall, which is concave (bifid?) at its lower ex- 
tremity, and almost fills up the aperture; a small, conical tooth 
placed near the peristome about midway between base and 
summit of aperture; two teeth, large and massive, placed deep 
in the throat, one, larger, situated near the umbilical region, 
and the other, smaller, placed near the parietal tooth; per- 
istome widely reflected, somewhat thickened, white, made con- 
tinuous by an elevated deposit of shell which connects the 
terminations; umbilicus small, open; the base of the shell has 
a sharp ridge or keel separating the umbilical region from the 
outer base of the shell (Fig. 6s). 
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