Abstract
Gypidula and Pentamarella are the only pentamerid genera that occur in the Cedar Valley formation. Individually and specifically they are sparsely represented as compared with either Atrypa or Stropheodonta. Their species, however, are among the more distinctive index fossils. The middle portion of the Littleton substage has two characteristic forms of Pentamarella and has been designated the pentamarella zone. Two peculiarities in stratigraphic distribution of these genera are notable. Gypidula is confined to the basal Independensis zone of the Cedar Valley, but appears in moderate numbers in the succeeding Devonian formations of the State. Pentamerella occurs in every zone of the formation but as yet has not recovered from superadjacent beds.
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