In 1973 and 1979, the geological and palaeontological reconnaissance surveys on the Mesozoic group of Los Andes Cordillera, Central Peru were carried out by the members of Palaeontological Party of Chiba University and of Instituto de Geologico, Minero y Metalurgico, Ministerio de Energia y Minas, INGEMMET, as the cooperative study supported by the Overseas Scientific Research Funds, Ministry of Education, Government of Japan. The Jurasso•Triassic marine sediments are distributed widely on the western foot and the midst of Los Andes Cordillera in the southern part of Peru. Some Jurassic trigoniids from this part are described in this paper as one of the results obtained by the cooperative study. The fossils treated in this paper were collected by the geologists of INGEMMET through the geological survey for making the geological sheet map of the southern part of Peru. Their fossils are ...