Berg‐Madsen, Vivianne & Peel, John S. 1978 04 IS: Middle Cambrian monoplacophorans from Bornholm and Australia, and the systematic position of the bellerophontiform molluscs Minute Middle Cambrian monoplacophorans originally reported from Australia are redescribed on the basis of material from the Kalby Clay of Bornholm. A recent classification of Bellerophon. Sinuites and related genera as monoplacophorans is discussed and rejected. Members of the group are returned to the Gastropoda on account of their similarity in ornament, musculature and inferred water circulation patterns, with contemporary fossil helically coiled gastropods. Water circulation patterns are deduced in Protowenella flemingi and support the assignment to the Monoplacophora. Kulhyella poulseni n.gen. n.sp. is described.

ABSTRACT. Type specimens of Hyolithus tenuistriatus

ABSTRACT. Re-examination of type specimens of Early Cambrian and early Mid Cambrian hyoliths from Sweden confirms placement of Hyolithes teretiusculus Linnarsson in Hexitheca Syssoiev, and reassignment to the order Hyolithida rather than Orthothecida. Inclusion of Hyolithes affinis Holm within Decoritheca Syssoiev is re-confirmed, and Hyolithes socialis Linnarsson is now referred to Nevadotheca Malinky and Slapylites Marek. An operculum included under Hyolithes oelandicus Holm is transferred provisionally to Maxilites Marek, and conchs of that species are placed under Tulenicornus Val'kov with question. No other hyolith species of Holm can be definitely assigned to genus. The rarity of well preserved opercula is a major impediment to recognizing hyolith taxa confidently, and we follow Holm in attributing the comparative rarity of opercula to the fact that in some hyolith taxa the operculum may have been composed of a different, and perhaps less stable, material than the rest of the conch.

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