LYMNyID.E OF NORTH AMERICA. 51 



specimens were killed when seventeen weeks old, the smallest speci- 

 men being 4 mill, long and the largest 27 mill. No reason is apparent 

 for the disparity in size. 



1. LENGTH OF LIFE. 



The duration of life in the family Lymnseidse is from three to 

 four years, full maturity being reached in about two years. Dr. Lyon 

 has successfully raised Galba reflexa until fifty-two weeks old, the 

 measurements at different stages of growth being as follows : 

 6 weeks; length, 2.00; width, 1.50 mill. 

 12 " " 5.00; " 2.75 " 



12 " " 10.00; " 5.00 " 



16 " " 13.00; " 6.00 " 



16 " " 20.50; " 7.50 " 



21 " " 21.50; " 9.00 



21 " " 25.00; " 9.00 " 



33 " " 26.50; " 9.50 " 



52 " " 26.00; " 11.50 " 



52 " " 28.50; " 10.50 " 



Radix auricularia was raised by Mr. Woodruff until four weeks 

 old, with the following result : 



When hatched, length 0.75; width .65 mill. 1^ whorls 1 

 12-24 hours old, " 2.20; " 1.10 " 2% " * 

 2 weeks " " 6.50; " 4.50 " 3 

 4 " " " 11.50; " 8.00 " 3% " 



m. BIBLIOGRAPHY. 1 



The following works have been consulted in the preparation of chapter II : 

 Adams, C. C, 1906. Andre, Emile, 1901. Baker, F. C, 1902; 1906, b. 

 Braun, M., 1888. Brot, A., 1877. Bunker, Robert, 1880. Call, R. E., 1884. 

 Chaster, G. W., 1899. Clessin, S., 1873, 1877, 1880. Cockerell, T. D. A., 1885. 

 Colton, H. S., 1908. Cooke, A. H., 1895. Crowther, H., 1896. Dall, W. H., 

 1896. DeVarigny, H., 1894. Fischer and Crosse, 1874. Fischer, Paul, 1883. 

 Forel, S. F. A., 1869 ; 1874. Friedel, Ernst, 1870. Gleason, H. A., 1909. Heyne- 

 mann, D. F., 1868. Hogg, Jabez, 1854 ; 1870. Jeff ery, W., 1882. Jones, K. H., 

 1899. Jordan, H., 1883; Jordan and Copeland, 1877. Lankester, E. R., 1874. 

 Leidy, J., 1887. Lewis, J., 1868, a. Linden, Maria, Grafin von, 1891. Martens, 

 E. von, 1899. Ortmann, A. E., 1909. Pauly, A., 1877. Pilsbry, H. A., 1896. 

 Ruthven, A. G., 1904. Semper, Carl, 1874; 1881. Siebold, C. Th. von, 1875. 

 Sterki, V., 1891, a. Stearns, R. E. C., 1900; 1901. Stubbs, A. G., 1898. Sykes, 

 E. R., 1894. Tryon, G. W., 1882. Walter, H. E., 1906.-^Whitfield, R. P., 1882. 

 Wiedersheim, Prof., 1879. Willem, V., 1896. Woodword, S. P., 1856. Young, 

 E., 1878. 



1 Shell white, vitreous, transparent. 



2 Columellar plait very prominent. 



8 Last whorl wide and shell globular. 



1 See the bibliography at the end of the volume. 



