192 THE CHICAGO ACADEMY OF SCIENCES. 
very decided swelling on the inner side, which is probably a modified 
entocone. The ninth tooth (transition) is distinctly tricuspid, while 
the tenth tooth is a typical marginal, the transition being very abrupt. 
The only radula of Lymnea known which is at all comparable 
with this species is Lymne@a hawaiensis' Pilsbry, described from Ha- 
wail, in which the laterals are modified in much the same manner, This 
species is very small and of a wholly different character and should 
probably be made the type of a distinct group of Lymnzas. The com- 
bination of the characters of the shell, radula and genitalia gives to 
this species a higher rank than a subgenus or section and entitles it 
to full generic consideration. 
Acella haldemani (“Deshayes,” Binney). Plate XVIII, figure 1; 
Plate XX VI, figures 1-4. 
Lymnea gracilis Jay, Cat., Ed. 3, p. 112, pl. i, figs. 10, 11, 1839, (non Zie- 
then, 1830) —WHEATLEY, Sh. U. S., p. 23, 1845.—Jay, Cat. Ed. 4, p. 269, 1852.— 
Lewis, Proc. Phil. Acad., 1856, p. 259; 1860, p. 18—ReEEvE, Elements of Conch., 
p. 179, 1860.—Lerwis, Proc. Bost. Soc. N. H., IX, p. 160, 1862—Morser, Amer. 
Nat., p. 651, pl. 11, fig. 6, 1870—Lerwts, Proc. Phil. Acad., 1872, p. 102.—SmiruH, 
Nautilus, XX, p. 91, 1907—Wa ker, Nautilus, XXII, p. 18, 1908; Journ. Conch., 
XII, p. 240, 1909. 
Lymnea_ gracilis DEKay, Cat. An. N. Y., p. 32, 1839.—Jay, Ann. N. Y. 
Lyc. N. H., IV, p. 170, 1846.—Currigr, Sh. Grand. Riv., Mich., 1859-—W uirtti1- 
MORE, Proc. Bos. Soc. N. H., VII, p. 151, 1859. 
Limnea gracilis C. B. ApAMs, Am. Journ. Sci., XL, p. 267, 1841; Thomp. 
Hist. Vt., pt. I, p. 153, 1842.—Strmpson, Sh. N. Eng., p. 52, 1851—Lewis, Proc. 
Bost. Soc. N. H., V, p: 296) 1856) Proc. Bost. Soc. N. H., VIj sp: 2) 1856-— 
Binney, Check List, p. 12, 1860—lDLarHam, Proc. Phil. Acad., 1860, p. 155.— 
Binney, L. and F. W. Sh. N. A., II, p. 69, figts. 113, 114, 1865; Journ. de Conch., 
XV, p. 427, 1867.—Currigr, Kent Sci. Inst. Mis. Pub., No. 1, 1868—Sowersy, 
Conch. Icon., XVIII, Limn. sp., 19, pl. 3, fig. 19, a, b, 1872—Tryon, Con. Hald. 
Mon., p. 114, 1872; Heron, Ottawa Nat., I, p. 39, pl. 11, fig. 4, 1880—FiscHER, 
Man. de Conch., p. 506, 1883.—Tryon, S. and S. Conch., III, p. 101, pl. 103, fig. 8, 
1884. BEAUCHAMP, L. and F. W. Sh. N. Y., p. 9, 1886.—Ottawa Nat., IV., p. 56, 
1890.—Tayvtor, Ottawa Nat. VI, p. 35, 1892—Watker, Nautilus, VI, p. 34, 1892 — 
MARSHALL, Rep. N. Y. State Mus., XLVII, p. 65, 1893—WatLkeErR, Rev. Moll. 
Mich., p. 18, 1894.—MARSHALL, Rep. N. Y. Col. Exp., p. 512, 1894.—SARGENT, 
Nautilus, IX, p. 127, 1896—WaAtkeEr, Nautilus, XII, pp. 119, 131, 1899.—LeErt- 
son, Bull. N. Y. State Mus., LXX XVIII, p. 56, 1905—CuHaApwick, Bull. Wis. Soc. 
N. H., N. S. IV, p. 83, 1906—Baxer, Science, N. S., XXVII, p. 943, 1908— 
Letson, Bull. Buf. Soc. Nat. Sci., IX, p. 242, 1909. 
Limnea gracilis HALDEMAN, Mon. Limn., p. 50, pl. 13, fig. 21, 1842.—NEw- 
BERRY, Proc. A. A. A. Sci., V, p. 105, 1851—LapHam, Trans. Wis. State Agr. 
Soc., II, p. 368, 1852—DrKay, Zool. N. Y., p. 70, pl. 4, fig. 73, 1843—MuzEs, 
Geol. Surv. Mich., 1860, p. 237. 
Limneus gracilis KtUster, Conch. Cab., p. 50, taf. 11, figs. 9, 10, 1862. 

1See Proc. Phil. Acad., 1903, p. 791, for figures. 
