Operculum of the early middle ordovician gastropod palliseria robusta

Yochelson, E.L.

Journal of Paleontology 60(3): 656-660


ISSN/ISBN: 0022-3360
DOI: 10.2307/1305051
Accession: 006036136

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A flat, thin, platelike operculum from the Antelope Valley Limestone of central Nevada [USA] fits the aperture of the shell of Palliseria robusta; abundance of these shells at the locality where the operculum occurs further supports its association with P. robusta. The operculum shows no evidence of spiral growth; its inner surface has one muscle prong. Palliseria shells are present in Nevada in enormous numbers, but opercula are known from only three localities. Because these platelike opercula are less robust than the coiled shells, most opercula may have been destroyed by wave and current movements after death of the animals.