166 THE CHICAGO ACADEMY OF SCIENCES. 



Limncea columella var. macrostoma WHITEAVES, Can. Nat. & Geol., VI, 

 p. 458, 1861; Can. Nat. & Geol., VIII, p. 102, 1863. 



Lymncea columella var macrostoma JAY, Cat., Ed. 4, p. 261, 1852. MORSE, 

 Amer. Nat., Ill, pi. 3, fig. 16, 1870. LERMOND, Shells of Maine, p. 37, 1908. 



Lymnea macrostoma DEKAY, Cat. An. N. Y., p. 32, 1839. GIRARD, Proc. 

 Nat. Inst., p. 81, 1856. TRYON, Amer. Journ. Conch., II, p. 11, 1866. 



Limn&a macrostoma GOULD, Invert. Mass., p. 217, fig. 148, 1841. TAYLOR 

 and SHIVERICK, Cat., 1840. PRESCOTT, Sh. Mass., No. 196, 1842. READ, Cat., 

 1845. RUSSELL, Journ. Essex Co. Nat. Hist. Soc., p. 130, 1852. TUFTS, Proc. 

 Essex Inst., I, p. 30, 1856. TRUE, Proc. Essex Inst., II, p. 195, 1857. Can. Nat. 

 & Geol., II, p. 198, figure, 1857. REEVE, Elements of Conch., p. 179, 1860. 

 BINNEY, Land & F. W. Sh. N. A., II, p. 34, fig. 39, 1865. TRYON, Amer. Journ. 

 Conch., Ill, p. 196, 1867. GOULD, Invert. Mass., ed. Binney, p. 472, f. 724, 1870. 

 TRYON, Con! Hald. Mon., p. 88 (62) pi. 16, fig. 2, 1872. SOWB., Conch. Icon., 

 XVIII, Lim., sp. 43, pi. 6, fig. 36, 1872. CR. and FISCH., Mis. Scient. Mex., Moll., 

 II, p. 52, 1880. 



Limnca macrostoma HALD, Mon. Limn., pi. 12, figs. 1-8, 1842. LAPHAM, 

 Trans. Wis. State Ag. Soc., II, p. 368, 1852. TUFTS, Cat. Mass. State Cab., p. 

 87, 1859. 



Limnaa merostoma RAVENEL, Cat. Sh. Cab. Ravenel, p. 11, 1834. 



Radix macrostoma HARTMAN and MICHENER, Conchologia Cestrica, p. 63, 

 fig. 120, 1874. 



Neristoma macrostoma TRYON, Amer. Journ. Conch., I, p. 248, 1865. 



Radix columella var. macrostoma PRIME, Forest & Stream, XV, p. 245, 

 1880. 



Limnaa acuminata C. B. ADS., Amer. Journ. Sci., XXXIX, p. 374, 1840. 



Lymncea columella var. acuminata JAY, Cat., ed. 4, p. 268, 1852. 



SHELL : Ovate, somewhat pointed, thin, fragile, transparent ; color 

 light greenish or yellowish horn ; surface shining, covered with rather 

 coarse growth lines, and encircled by heavily impressed spiral lines; 

 whorls four, well rounded, rapidly enlarging, the last one three times 

 the size of the rest of the shell ; spire sharply conic, rather short ; apex 

 small, very dark brown ; sutures tightly appressed ; a ridge is fre- 

 quently formed at the suture where the lines of growth meet the whorl 

 above ; aperture ovate, dilated, expanded at the lower part ; peristome 

 thin, acute ; inner lip closely appressed to the body whorl and reflected 

 over the umbilicus, either completely closing the latter or leaving a 

 small, narrow chink; axis slightly twisted; the columellar region is 

 so narrow and so peculiarly arched that a view may be taken from 

 the base nearly to the apex, as in Succinea retusa; this is especially 

 noticeable in the wide shells called macrostoma. The nuclear whorls 

 do not differ in outline from those of Lymncea stagnalis. The nucleus 

 consists of about 1^ smooth whorls. The growth lines are very heavy 

 at the beginning of the post nuclear shell. 



