LONDON. Zoological Society, April 9.—Dr. A. Smith Woodward, vice-president, in the chair.—Miss J. Proctor: The variation of. the pit-viper, Lachesis atrox. The paper idelalt with the variation of the principal characters of the Central and South American pit-viper, Lachesis atrox, L., of which the author regarded L. lanceolatus, Lacép., as a synonym, and L. affinis, Gray, jararaca, Wied, and jararacussu, Lacerda, as varieties. The author laid special stress on the different patterns of markings, discussing their evolution and regarding that shown by the more northern form, L. affinis, as the most primitive, from which all others could be derived.