"A detailed description is given of the internal anatomy of the Devonian spiriferid brachiopod Spinocyrtia iowensis (Owen). . . . Special consideration is given to the growth lamellae within the shell, which suggest the mode of formation of the dental plates, delthyrial plate, teeth, and hinge plates. Comparisons are made with other Devonian spiriferids. Many of the shells are shown to be asymmetrical both externally and internally."

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