168 THE CHICAGO ACADEMY OF SCIENCES. 
central tooth witha base of attachment longer than wide, the 
base excavated and the lower outer corners much expanded; re- 
flection tricuspid, the central cusp long and wide, very nearly 
reaching the lower margin of the base of attachment, side 
cusps very short; lateral teeth similar to the central tooth, but 
bicuspid, the inner cusp much the larger; marginals variable, 
at first similar to laterals, but soon the inner cusp (twenty ) be- 
comes bifid, changes into a perfect cusp (twenty-three trifid), 
and finally the reflection becomes very narrow and with three 
cusps, of which the central one is the largest (Fig.27). There 
are about 100 rows of teeth. Binney gives 21-1-21 and Morse 
28-1-28 teeth. 
Genitaa: ‘‘The characteristic feature of the genitalia is 
the penis sac. It is unproportionally long, club-shaped, and 
greatly enlarged above, where it receives both vas deferens 
and retractor muscle. The genital bladder is small, elongate- 
Fre. 27: 
Radula of POLYGYRA MONODON FRATERNA Say. (Original.) c, central 
tooth; 11, first marginal tooth; 16, 17,20, intermediate marginal teeth; 23, 
27, 29, outer marginal teeth. 
oval, on a short, delicate duct. The epididymis is convoluted 
in its whole length.” (W.G. Binney.) 
Distribution: Canada to Minnesota, south to North Caro- 
lina and San Antonio, Tex. (Pilsbry.) 
Geological distribution: Pleistocene of the Mississippi Val- 
ley; Loess. 
FHlabitat: Found sparingly under pieces of bark, chips, logs, 
etc.,in open patches of woodland or in meadows. The variety 
in this area does not congregate together but is found either 
singly or with one or two companions. Associated sometimes 
with P. éhyroides and Pyramidula alternata. 
- 
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ty 52), err, <1 
