Cyclopygid Trilobites from the Ordovician Builth-Llandrindod Inlier, Central Wales

Cyclopygids are a minor element in the abundant trilobite fauna of the Ordovician Llanfawr Mudstones Formation ( teretiusculus – gracilis biozones) of the Builth-Llandrindod inlier. The rarity of these trilobites may be due to the accumulation of these sediments close to the shoreward limit of their depth range, and if this is the case, their presence, together with sedimentological evidence, can be used to infer the bathymetric limits within which the Llanfawr Mudstones Formation might have been deposited. Species of Degamella , Microparia ( Microparia ), Microparia ( Heterocyclopyge ), Sagavia and Emmrichops are described; some are common to the Dobrotivá Formation in Bohemia, whilst others have affinities with species from approximately coeval strata in Kazakhstan and north-west China.