Fifteen species of Late Permian bryozoans occur in a biohermal bank in the Mission Argillite of northeastern Washington. These include two species conspecific with species described from Japan and 13 new species, one of which is the type species of a new genus.

Tectonostratigraphic terranes thought to be allochthonous to North America include the Eastern Klamath terrane in northern California, the Quesnellia terrane in northeastern Washington and southern British Columbia, and the Slide Mountain terrane in northern British Columbia (Monger and Berg, 1987; and Silberling et al., 1987). Ross and Ross (1983) cited fusulinid occurrences in these terranes as evidence for a southern geographic origin, and concluded that their present widespread occurrences in the western Cordillera were the result of allochthonous terranes being accreted to North America during the Mesozoic. The presence of two species of bryozoans, Dyscritella iwaizakiensis Sakagami, 1961, and Hayasakapora cf. erectoradiata Sakagami, 1960, previously reported from Japan, and the similarity of new species of bryozoans with those previously described from Japan, China and Russia supports the idea that these rocks were originally deposited in the southeastern or central western Pacific Ocean and subsequently accreted to the North American Plate.

Bryozoans and previously reported fusulinids indicate that the biohermal bank is latest Wordian (Kazanian).