Stratigraphy of the Ordovician Maravillas Formation
Study of the bryozoan fauna of the Ordovician Maravilllas Formation in trans-Pecos Texas indicates that the major portion of the formation is of Richmondian age. Exact correlation with the type Ordovician section appears somewhat uncertain, and the fauna is best considered as mixed. The twenty-six species described, including three which are new, are contained in twenty-two genera. More of the described species occur In the Fernvale Formation of the upper Mississippi Valley than In any other horizon. These include Anaphragma mirabile. Constellaria polystomella, Cyphotrypa wilmingtonensis. Phaenopora wilmingtonensis, and Sceptropora facula.
Hallopora subnodosa and Rhombotrypa subquadrata are characteristic of those portions of the formation which contain bryazoans.
A tentative occurrence chart is included, but further studies will undoubtedly produce many alterations in the chart.