An exceptionally well-preserved and diverse Monotis fauna is described from the Upper Pardonet Formation of the Schooler Creek Group. In collections from 8 limestone beds, ranging from the base to the top of the 145-ft thick section, 6 abundant species and subspecies of Monotis are distinguished. Monotis subcircularis Gabb is redescribed and a neotype chosen from numerous topotypes. The species succession of Monotis is, in descending order: bed "h": Monotis ochotica (Keys) posteroplana West., n. subsp., beds "f"+"g": M. subcircularis Gabb (+ M. cf. M. ochotica posteroplana in "g"); bed "e": M. callazonensis West., n. sp. + M. jakutica (Teller); bed "d": M. ochotica densistriata (Teller); bed "b"+"c": M. scutiformis Teller pinensis West., n. subsp.; bed "a": M. n. sp.? aff. M. scutiformis. Below bed "a" the Himavatites Zone with M. cf. M. scutiformis is inferred. Monotis of the M. scutiformis group is known from America N. of the 51st parallel only and from eastern Asia, and always antedates Monotis of the M. ochotica-subcircularis group. These 2 groups are of middle and late Norian Age, respectively. A more detailed correlation is possible with the Monotis succession of south Japan. Only M. subcircularis has its main distribution in the Americas while the other abundant forms probably originate in eastern Asia. M. subcircularis geographically replaces the Asian M. ochotica during most of its duration. There are also slight Alpine affinities with the rare M. n. sp.? aff. M. inaequivalvis Bronn and M. cf. M. hoernesi Kittl. No stratigraphic equivalents of beds "d", "e," and "h" are known from other sections of British Columbia, but bed "e" may possibly correlate with the base of thick Monotis-bearing sequences in Nevada. Thus Monotis seems to be restricted to the Upper Norian in the U. S. and perhaps also in the whole southern hemisphere. Monotis may have lived attached to seaweeds in shallow, almost stagnant water, probably of a geographically somewhat restricted marine embayment or basin. Because almost equivalve and strongly inequivalve shells are often found associated, regional environmental factors were not the dominant cause for differences in inflation, and these differences are not due to ecological adaptation, i. e., modification of broadly varying species. This does not exclude the preference of certain species for certain biotopes. Statistics are employed to display the variations in 6 to 8 measured characters of the valves and to assist in the taxonomy. For each faunule (sample) characteristic measurements are plotted in frequency polygons and binomial and trinomial scatter diagrams. Reduced major axes, means, standard deviations and -errors, correlation- and dispersion-coefficients are calculated. The associated invertebrate fauna is briefly described; it consists mainly of benthonic pelecypods which are restricted to a small number of beds. Among the rare ammonites is Choristoceras n. sp. aff. C. kellyi Smith.