234 THE CHICAGO ACADEMY OF SCIENCES. 



Geological distribution : Pleistocene; Loess. 



Habitat: Found in stations similar to the other Pupidae. 



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 contracfa. 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, pi. xxx, fig. 8. 



Pupa contracta SAY, Journ. Phil. Acad., Vol. II, p. 374, 1822. 

 Pupa deltostoma CHARPENTIER in CHEMNITZ, ed. 2, p. 181, pi. 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. 353^.) 



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. 65). 



