The morphology of the Late Ordovician solutan Dendrocystites is reevaluated based on more than 300 specimens from the Letná and Zahořany formations (Prague Basin, Czech Republic). This genus is reported for the first time from the Bohdalec Formation, and its presence is confirmed in the Vinice Formation. The morphology of all specimens of the stratigraphically older species D. barrandei (Sandbian) is identical to that of small to medium-size individuals of D. sedgwicki (Katian). Distinctive characters of D. sedgwicki occur only in the largest specimens, and are all size-related (more asymmetrical thecal outlines, stronger ornamentation, rosetting pattern of thecal plates, proliferation of platelets in the proxistele). Consequently, the transition from D. barrandei to D. sedgwicki is interpreted as the result of heterochronic processes, with the largest individuals of D. sedgwicki displaying hyperadult morphologies (hypermorphosis). Dendrocystites is locally abundant in both the Letná and Zahořany formations, but extremely rare in the deeper deposits of the Vinice and Bohdalec formations. This pattern coincides closely with first order fluctuations of the sea-level in the Prague Basin. The life orientation and implied feeding strategy of Dendrocystites and other solutans are both critically discussed. Several independent lines of evidence suggest that solutans were more likely detritus-feeders. Finally, it is proposed that two morphologically distinct patterns of dististele organization were elaborated independently from the polyplated, undifferentiated stalk-like appendage of Coleicarpus (plesiomorphic condition). Consequently, a major subdivision of the class Soluta into two main clades (Dendrocystitida ord. nov. and Syringocrinida ord. nov.) is proposed. The monophyly of each order is supported by apomorphies based primarily on the organization of the dististele and the morphology of the periproct. "Dendrocystites" rossicus is reinterpreted as belonging to an unknown genus of syringocrinids, whereas Heckericystis kuckersiana may represent a third species of Dendrocystites. •

Abstract.-The primitive blastozoan Felbabkacystis luckae n. gen. n. sp. is described from the Drumian Jince Formation, Barrandian area (Czech Republic) from eleven fairly well-preserved specimens. Its unique body plan organization is composed of a relatively long, stalk-like imbricate structure directly connected to the aboral imbricate cup of the test and of an adoral vaulted tessellate test supporting the ambulacral and brachiolar systems. Its bipartite test, called prototheca, highlights the evolution of the body wall among blastozoans. Felbabkacystis n. gen. shows the combination of plesiomorphic (imbricate stalk-like appendage) and derived features (highly domed peristome, elongate epispires). The new genus is interpreted as a transitional form between calyx-bearing and theca-bearing blastozoans, and is attributed to the new family Felbabkacystidae. The lithology, the associated fauna, and the possession of a long stalk suggest that Felbabkacystis was probably a low-level suspension feeder living in relatively deep settings.

Anomalocystitid mitrates represent one of the most diverse and long ranging clade of stylophorans (Early Ordovician-Middle Devonian). Although they probably originated from a peri-Gondwanan stock of early mitrocystitids during the Floian, the fossil record of anomalocystitids in the Middle-Upper Ordovician of the Mediterranean Province remains extremely scarce and largely underestimated. The unusually shaped anomalocystitid genus Diamphidiocystis was originally described in the latest Katian-Hirnantian of North America (Illinois). However, earlier occurrences of this genus in the late Darriwilian of western France (Brittany) suggest a probable peri-Gondwanan origin. Based on new Middle to Late Ordovician material from the Anti-Atlas (Morocco), Bohemia (Czech Republic) and Brittany (France), all occurrences of Mediterranean Diamphidiocystis are considered as conspecific and formally described as D. regnaulti sp. nov.. The palaeobiogeographic significance of Ordovician anomalocystitid mitrates is discussed.

Cornute stylophorans are a minor, though typical component of Middle-Late Ordovician echinoderm assemblages adapted to soft siliciclastic substrates, in high latitude peri-Gondwanan regions. All previously reported occurrences of Darriwilian-Katian cornutes from Czech Republic, France, Morocco and Spain are revised and their plate homologies reassessed. The genera Beryllia and Juliaecarpus are reinterpreted as junior synonyms of Domfrontia, and Thoralicystis is synonymised with Bohemiaecystis. Several Mediterranean scotiaecystids previously assigned to Bohemiaecystis and/or Scotiaecystis are placed within Thoralicarpus gen. nov., and cornute taxa originally left in open nomenclature by Chauvel are formally described as Bohemiaecystis chouberti sp. nov. (AVI) and Destombesicarpus izegguirenensis gen. et sp. nov. (AVIII). Other new Mediterranean taxa include Arauricystis clariondi sp. nov., Destombesicarpus budili gen. et sp. nov., Milonicystis reboulorum sp. nov., Thoralicarpus bounemrouensis gen. et sp. nov., and T. prokopi gen. et sp. nov. The six cornute genera identified in Darriwilian-Katian Moroccan echinoderm Lagerstätten are also present in coeval assemblages of at least one other Mediterranean region, thus supporting the existence of strong faunal affinities between the Anti-Atlas, the Armorican Massif, the Barrandian area and the Iberian Peninsula.

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