The silicified gastropod fauna from the excellent Tonoloway reference section at Pinto in western Maryland has been studied by means of specimens obtained by etching bulk samples in hydrochloric acid. Of the four published gastropod taxa from this locality, three are placed in synonymy and one, based on an indeterminate internal mold, is restricted to its type. In addition to the aforementioned taxa, a new genus and species of Bellerophontacea in the subfamily Carinaropsinae and two species of Holopeid gastropods were recovered and described. Sedimentary and petrographic data suggest a low-intertidal to shallow-subtidal, soft-bottom, carbonate substrate environment for the gastropod-bearing beds sampled. This interpretation is supported by data from several studies of the paleoecology of Paleozoic gastropods which are systematically related and morphologically similar to the taxa recovered in this study.

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