Extensive silicified faunules of Middle and Late Ordovician sphinctozoan sponges have been assembled from the northern part of the eastern Klamath Mountains in northern California. The sponges are from eugeosynclinal rocks that are the westernmost Middle Ordovician to Late Devonian rocks at that latitude in North America. Seventeen new species occur in the assemblages, including 10 porate and 7 aporate forms. New genera of porate forms are Amblysiphonelloides and Corymbospongia, and new porate species include: Amblysiphonella grossa, Amblysiphonelloides tubula, A. reticulata, Imperatoria mega, I. media, I. minima, I. irregularis, Corymbospongia adnata, C. mica, and C.(?) perforata. These are the first reported occurrences of Amblysiphonella and Imperatoria in the Ordovician. New aporate genera are Cystothalamiella and Porefieldia, and new aporate species include: Cystothalamiella ducta, C. craticula, C. tuboides, Porefieldia robusta, Girtyocoelia epiporata, and G. canna. This is the oldest known occurrence of Girtyocoelia, which is generally considered a Late Paleozoic form. Cliefdenella obconica n. sp. is characterized by an obconical growth form in contrast to other species of the genus that are more massive or explanate. Cliefdenella is considered here as an imperforate sphinctozoan.

Minor isolated hexactines and hexactine-derived spicules of Hexactinellida were associated with the sphinctozoans. No particular taxa within the class can be distinguished from these individual elements.