Two oribatid mite species of the family Peloppiidae (Acari, Oribatei) from Mongolia

The new of oribatid mites, Metrioppia krivolutskyi sp. n., from Mongolia is described. It is somewhat similar to M. zlotini Krivolutsky, 1971 and M. helvetica Grandjean, 1931. However, the new species is readily distinguishable from the aforementioned species in the relatively short interlamellar setae, the presence of well-developed insertions of 9 pairs of notogastral setae (setae p(1), P-2, and P-3 are distinctly developed), the relatively short and blunt rostral teeth and the narrower and shorter lamellae which do not reach the rostrum tip. The known species of oribatid mites, Ceratoppia bipilis (Hermann, 1804), registered in the fauna of Mongolia for the first time, was redescribed. The features of Mongolian specimens are almost consistent with European and Asian ones. There are some differences between them. In Mongolian species lamellae is a bit longer, insertion of notogastral seta h(1) is rather well-developed, anterior margin of notogaster is rounded and the humeral projection is poorly developed.