THE NATURAL HISTORY SURVEY. 167 
central tooth as in var. fraterna ; lateral teeth similar to those in 
var. fraterna, the inner cusp becoming elongated toward the 
tenth tooth; marginal teeth similar to those of var. fraterna, but 
the last three teeth with three outer cusps and two inner cusps, 
the second from the left being much the larger. There are 
about Ioo rows of teeth. 
Genitalia: See var. fraterna. 
Distribution: Ohio and Michigan to Minnesota, south to 
Nashville, Tenn., and Neosho County, Kan. (Pilsbry.) 
Geological distribution: Pleistocene of the Mississippi Val- 
ley; Loess. ! 
Habitat: Found under dead logs and chips in most locali- 
ties, Associated with Gastrodonta arborea, Vitrea electrina, Pyra- 
midula striatella, etc. 
Remarks: This species is distinguished from all others 
found in the area by its white, entire peristome, large parietal 
tooth and its (generally) open umbilicus. In a recent paper 
(Proc. Phil. Acad., 1900, p. 454), Mr. Pilsbry has rearranged 
the nomenclature of this species, making the shell formerly 
known as ‘‘/eaii Ward” the typical Monodon, the forms hereto- 
fore known under that name becoming variety fraterna. Mon- 
odon is one of our most common species and is generally found 
in little colonies of from six to a dozen or fifteen individuals. 
It has been collected in the southern and western regions only, 
but will no doubt be found in the northern. 
62a. Polygyra monodon fraterna Say, pl. xxx, fig. 3. 
Helix fraterna Say, Long’s Exped., Vol. II, p. 257, pl. xv, fig. 3, 1824 
Shell; Differing from Monodon in being larger, more hir- 
sute, in having the umbilicus frequently partly closed or wholly 
imperforate and in being less convex than the type. 
Greater diameter, 11.50; lesser, 10.50; height, 7.50 mill. (9964.) 
a 4 TOO eS UO ee 00%. (9964.) 
i < 10,005. > 4"? Ors 8 "7.00. * +. (8449.) 
Animal; With a long, narrow and cylindrical foot, trun- 
cated: before and pointed behind; color yellowish-white on 
foot and sides of body, darker on head, tentacles, eye-pedun- 
cles and top of head; eye-peduncles very long, cylindrical; 
tentacles short, blunt; foot 22 mill. long, 5.50 mill. wide. Heart 
pulsations regular, one hundred per minute. The pustules on 
the body stand out very prominently. 
Faw: As in Monodon with seven ribs. 
Radula formula: 414+4+4+4,°+4+42+ 4+ (31-—1—31); 
