A single specimen of Ratcliffespongia wheeleri n. sp. from the upper part of the Middle Cambrian Wheeler Shale in the Drum Mountains of western Utah shows two distinct skeletal layers in the limonite-replaced fragment. The probable inner layer has large, circular to elliptical parietal gaps, some of which are aligned horizontally(?); gaps are outlined by long rays of hexactine-based spicules in irregular orientation and spacing. The probable outer layer has several ranks of stauracts in regular reticulation and ranking, all at approximately 45 degrees to the probably horizontal direction. The specimen is part of a probably shallow turbidite-transported assemblage from the margin of the House Range embayment.

A diverse assemblage of Middle Cambrian sponges, recently collected from the Wheeler and Marjum Formations of western Millard County, Utah, includes a variety of demosponges and hexactinellids. This collection includes the verongiid Vauxia bellula Walcott, 1920, and the protomonaxonids Choia carteri and Choia ridleyi Walcott, 1920, Hamptonia bowerbanki Walcott, 1920, and Hamptonia parva n. sp. Hexactinellids in the collection include the reticulosid protospongioids Diagoniella hindei Walcott, 1920, and Diagoniella magna n. sp.; the dierespongioid hydnodictyid Valospongia? gigantus Rigby, 1973; and the hintzespongioid Hintzespongia bilamina Rigby and Gutschick, 1976. A specimen of the problematic Sentinelia? draco Walcott, 1920, is also documented as part of the collection.

The calcareous heteractinid sponge Wewokella solida Girty, 1911, is reported from Colorado for the first time. Triactine-based skeletons are well preserved and dermal and gastral layers are composed of smaller spicules than those in the main wall of the many specimens. A fragment of an unnamed demosponge, possibly related to Heliospongia Girty, 1908, and fragments of root tufts occur with Wewokella in the Middle Pennsylvanian Minturn Formation near McCoy, in Eagle County, Colorado.

Conical and vase-shaped calathids are found in the Lower Ordovician Fillmore Formation of western Utah associated with intraformational conglomerates and small patch reefs. Calathium yersini n. sp. exhibits patterns of both the inner and outer walls of calathid two-wall construction. The broadly annulate walls are constructed from meroms with fused proximal merom feet forming the inner wall. The reticulate-patterned outer wall is formed by interlocking stellate ribs at the distal end of each merom. Latitudinal (horizontal) ribs interlock adjacent merom ribs side by side at the tips of ribs while meridional (vertical) ribs overlap merom shaft to merom shaft. Inner and outer walls are perforate. Pore-canal casts preserved in silicified molds suggest an exit and entrance current circulation for inner and outer wall pores. Upper ends of the calathids are not preserved, but an open cup is interpreted from infill material and encrustation of the interior cup wall by epibionts. Epibionts commonly encrust and thicken Calathium outer walls, with the cyanobacterium Girvanella as the dominant encrusting organism. Calathium yersini n. sp., among the earliest of receptaculitids, has a morphology suitable for water circulation consistent with that of filter-feeding organisms.

Lithistid orchoclad sponges within the family Anthaspidellidae Ulrich in Miller, 1889 include several genera that added ornate features to their outer-wall surfaces during Early Ordovician sponge radiation. Ornamented anthaspidellid sponges commonly constructed annulated or irregularly to regularly spaced transverse ridge-and-trough features on their outer-wall surfaces without proportionately increasing the size of their internal wall or gastral surfaces. This efficient technique of modifying only the sponge's outer surface without enlarging its entire skeletal frame conserved the sponge's constructional energy while increasing outer-wall surface-to-fluid exposure for greater intake of nutrient bearing currents. Sponges with widely spaced ridge-and-trough ornament dimensions predominated in high-energy settings. Widely spaced ridges and troughs may have given the sponge hydrodynamic benefits in high wave force settings. Ornamented sponges with narrowly spaced ridge-andtrough dimensions are found in high energy paleoenvironments but also occupied moderate to low-energy settings, where their surface-to-fluid exposure per unit area exceeded that of sponges with widely spaced surface ornamentations.

Emeraldella is a rare arthropod of relatively large body size that belongs with the trilobite-like arthropods, Artiopoda. E. brutoni n. sp. from the Wheeler Formation of west-central Utah is the second species described and marks the first confirmed occurrence of Emeraldella outside the Burgess Shale of British Columbia. An articulated, flagelliform telson, similar to that of the Burgess Shale taxon Molaria, is recognized in Emeraldella. Evidence for the presence of lamellae on the exopods of Molaria is presented, supporting affinity of that taxon with Artiopoda. A close relationship between Emeraldella and Molaria is tentatively suggested, based on the morphology of tergites and telson.