LYMNEIDZ OF NORTH AMERICA. 179 
form, the posterior portion long, narrow and ribbon-like. Female or- 
gans not differing materially from those of Lymnea (pl. X, fig. ©). 
Disrripution: Holarctic region of . Europe; introduced into 
America.” 
This genus differs from all other known groups of Lymnzeidze 
in the very long and narrow penis which can scarcely be differentiated 
from the vas deferens. There is a different disposition of the retrac- 
tor muscles, especially in the form of the penis-sac insertions, and the 
prostate is more regularly pyriform and totally unlike any of the 
other groups. The vas deferens is also very long. The shell is pecu- 
liar in its strongly twisted columella and in its ample and expanded 
body whorl and its perforated (often wide) umbilical chink. Until the 
anatomy of more of the Lymnzas is known, the position of some species 
must remain doubtful. Lymnea randolphi Baker has been placed by 
Dr. Dall in Radix and the shell certainly has many characteristics in 
common with auricularia, but its position will remain doubtful until 
the animal is examined. Its position at the present time is thought to 
be with Stagnicola. 
1Radix auricularia (Linné). Plate XXII, figures 12-10. 
Helix auricularia Linne, Syst. Nat., Ed. X, p. 774, 1758.—BAKER, Science, 
n. s., XXVIII, p. 943, 1908. 
Limnea auricularia Mog.-TAnp., Hist. Moll. Fr., Il, p. 462, pl. 33, fig. 21-31, 
1855.—Crr. Rep: Brit. Ass., 1856, p. 992—Binney, L. & F. W. Sh. N. A,, II, 
p. 31, fig. 35, 1865.—BAKER, Nautilus, XV, p. 59, 1901—Nautilus, XVI, p. 58, 
1902; Moll. Chi. Area, II, p. 408, fig. 138, 1902.—CALL., Science, XVI, p. 65, 
1902.—Letson, Bull. N. Y. State Mus., LXXXVIII, p. 52, 1905—Wueat, Bull. 
Brook. Conch. Club, I, p. 10, 1907. 
Lymnea auricularia BAKER, Amer. Nat., XXIX, p. 675, fig. 10, 1905; Bull. 
Ill. State Lab. N. H., VII, p. 102, 1906. 
SueLL: Roundly ovate, inflated, thin; periostracum horn-color 
to pale gold; surface shining, lines of growth fine, wavy, crowded, with 
occasionally a heavy ridge representing a rest period ; spiral, impressed 
lines present but very fine; whorls four, convex, inflated, the last large 
and spreading; spire short, conic, very small compared with the body 
whorl; sutures deeply impressed, channeled in some specimens; aper- 
ture very large, ovate, occupying four- fifths of the length of the entire 
shell, rounded above and flaring below in old specimens ; peristome 
thin, sharp; columella sigmoid, the axis strongly twisted forming an 
erect, sharp ascending plait; callus very thin, closely appressed to the 
aUntil the anatomy of all the American species is known, the distribution 
of Radix must remain uncertain. At present, no American species is known 
which can be placed in this group. 
1Although this species is not native to America, it has been thought best 
to include a full description as it is the type of the genus and has also been 
introduced into a number of our greenhouses, No attempt has been made to 
include the Huropean synonymy. 
