Brachiopods and sponges from the Mazourka Formation permit refinement of previous Chazyan age terminations of this formation. Faunal elements described in this study indicate deposition starting in the Anomalorthis zone and possibly extending into the Rhysostrophia zone of Cooper's Whiterock stage. Sponges include Nevadocoelia cf. N. pulchra Bassler, Lissocoelia ramosa Bassler, Calycocoelia typicalis Bassler, Patellispongia cf. P. oculata Bassler, and Hesperocoelia undulata Bassler; all either conspecific or closely related to species described by Bassler from central Nevada. In addition Nevadocoelia mazourkaensis n. sp., Calcycocoelia inyoensis n. sp., and Streptosolen sp. occur in the fauna. At present these sponges are useful for correlation within the Great Basin only, but additional work may uncover species related to those of the type Chazyan or perhaps intermediate between those of the type Chazyan and Canadian. Other fossils include Mastopora(?) sp., Orthambonites eucharis, 0. minusculus, Plectorthis mazourkaensis, P. patula, and Rhysostrophia cf. R. occidentalis.