Abstract

Several hundred silicified specimens of Pleurotomaria canadensis Billings, 1865 and other rare fossils indicative of a late Canadian age have been collected from the Oxford Formation, southwest of Ottawa, Ontario. Redescription of this neglected gastropod species permits its assignment to the genus Ceratopea, even though no ceratopean opercula have been found.Rare faunal elements include ribeirioids and open coiled gastropods that may have lived, respectively, in and on a mud bottom. There is no evidence that they have been transported. It is suggested that Ceratopea canadensis lived on algal mats some distance away from the shore and from where it is now found. After death, the soft parts of this gastropod decayed and the heavy operculum rotted off. The lightened shell, filled with gas, floated shoreward, likely under conditions of relatively calm water. Discovery of opercula within the Oxford Formation would provide evidence to support this hypothesis.

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