192 THE CHICAGO ACADEMY OF SCIENi 



very decided .-welling on the inner side, which i- 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 Lymncca known which is at all comparable 

 with this species is Lymncca hawaiensis 1 Pilsbry, described from Ha- 

 waii, 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 Lymnaeas. The com- 

 bination of the characters of the shell, radula and genitalia give; 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 XXVI, figures 1-4. 



Lymncca gracilis Jay, Cat.. Ed. 3. p. 112, pi. i, figs. 10. 11, 1839. (non Zie- 

 then, 1330).— Wheat lev, Sh. U. S., p. 23, 1845.— Jav. Cat. Ed. 4. p. 269, 1352.— 

 Lewis, Proc. Phil. Acad., 1856, p. 259; 1860, p. 18. — Reeve, Elements of Conch., 

 p. 179, I860.— Lewis. Proc. Bost. Soc. N. H., IX, p. 160, 1862.— Morse, Amer. 

 Xat., p. 651, pi. 11, fig. 6, 1870.— Lewis, Proc. Phil. Acad., 1372. p. 102.— Smith, 

 Nautilus, XX, p. 91, 1907.— Walker, Nautilus, XXII. p. 18, 1908 ; Journ. Conch.; 

 XII. p. 240, 1909. 



Lymnea gracilis DeKay, Cat. An. X. Y., p. 32, 1339.— Jav, Ann. X. Y. 

 Lye. X. H., IV, p. 170, 1846.— Currier, Sh. Grand. Riv., Mich., 1859.— Whitti- 

 more, Proc. Bos. Soc. X. H., VII, p. 151. 1859. 



Limhcea gracilis C. B. Adams, Am. Journ. Sci., XL, p. 267, 1841; Thomp. 

 Hist. Vt., pt. I, p. 153, 1842.— Stimpsox, Sh. X. Eng., p. 52, 1S51.— Lewis, Proc. 

 Bost. Soc. X. H., Y, p. 296, 1856: Proc. Bost. Soc. X. H.. YI. p. 2. 13->3.— 

 Binney, Check List, p. 12, I860. — Latham, Proc. Phil! Acad., 1860, p. 155. — 

 Binney, L. and F. W. Sh. X. A., II. p. 69, figs. 113, 114, 1865: Journ. de Conch., 

 XV, p. 427, 1367.— Currier, Kent Sci. Inst. Mis. Pub., Xo. 1. 1868.— Sowerby, 

 Conch. Icon., XVIII, Limn, sp., 19, pi. 3, fig. 19, a, b, 1872.— Tryox, Con. Hald. 

 Mon., p. 114, 1872; Herox, Ottawa Xat.. I, p. 39, pi. 11, fig. 4, 1880.— Fischer, 

 Man. de Conch., p. 506, 1883.— Tryox, S. and S. Conch., Ill, p. 101. pi. 103, fig. 8, 

 1884.— Beauchamp, L. and F. W. Sh. X. Y., p. 9, 1886.— Ottawa Xat.. IV., p. 56, 

 1890.— Taylor, Ottawa Xat. VI, p. 35, 1892.— Walker, Xautilus, VI, p. 34. 1892.— 

 Marshall, Rep. X. Y. State Mus.. XLYII, p. 6.5. 1S93.— Walker, Rev. Moll. 

 Mich., p. 18, 1894.— Marshall, Rep. X. Y. Col. Exp., p. 512. 1394.— Sargext, 

 Xautilus. IX, p. 127, 1896.— Walker, Xautilus. XII, pp. 119, 131, 1S99.— Let- 

 sox, Bull. X. Y. State Mus., LXXXYIII, p. 56, 1905.— Chadwick, Bull. Wis. Soc. 

 X. H.. X. S. IV, p. 83, 1906.— Baker, Science. X. S.. XXVII, p. 943, 1908.— 

 Letsox, Bull. Buf. Soc. Xat. Sci., IX, p. 242, 1909. 



Limnea gracilis Haldemax, Mon. Limn., p. 50, pi. 13, fig. 21. 1342. — Xew- 

 eerry, Proc. A. A. A. Sci.. V, p. 105, 1851.— Lapham, Trans. Wis. State Agr. 

 Soc, II, p. 368, 1852.— DeKay, Zool. X. Y., p. 70. pi. 4. fig. 73. 1343.— Miles, 

 Geol. Sun-. Mich., 1860, p. 237. 



Limnceus gracilis Kuster, Conch. Cab., p. 50, taf. 11. figs. 9, 10, 1862. 



^ee Proc. Phil. Acad., 1903, p. 791, for figures. 



