THE NATURAL HISTORY SURVEY. 167 



central tooth as in var .fraterna ; lateral teeth similar to those in 

 \&r. 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 loo 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 Ga strodonta 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 "lean 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. 

 62 a. Polygyra monodon fraterna Say, pi. xxx, fig. 3. 



Helix fraterna SAY, Long's Exped., Vol. II, p. 257, pi. 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.) 

 11.00; " 10.00; " 7.00 " (9964.) 

 10.00; " 9.00; " 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. 



Jaw : As in Monodon with seven ribs. 



Radula formula : > + \ + Y- +i ++i+ V (3 1 - I - 3 1 ) J 



