Mining engineer, palaeontologist, Corresponding Member of the Russian Academy of Sciences, Professor, Director of the St. Petersburg Mining Institute (1893-1900). He investigated trilobites, brachiopods, foraminifera. He developed a new method and means of palaeontological research in transparent thin sections (1877). He conducted geological investigations in the field of the Carboniferous and Permian stratigraphy; substantiated the three-membered division of the Carboniferous. He proposed a scheme of the main Carboniferous units, which received an international vocation (1878); paid much attention to geological surveying. In 1885 – 1893, he was the head of the Office of the mountain unit of the Caucasus region. Elected a member of the Geographical and Mineralogical societies, awarded the Academician Brandt prize.