Acetic acid residue of samples of Silurian Chimney Hill Limestone from Oklahoma contain phosphatic brachiopods that are described as 2 new genera, Artiotreta and Acrotretella, and 2 new species, Artiotreta parva and Acrotretella siluriana. All of these are referable to the Order Neotremata. They may be referable to the family Acrotretidae, or they may represent a new family. Hundreds of perfectly preserved specimens of both valves of Artiotreta were examined, and all of them measured near 0.50 mm. in maximum diameter. All evidence indicates that they represent mature specimens and that they are not juvenile specimens. Only 24 Acrotretella were found. Specimens were collected in 3 localities 2 to 10 mi. apart. Both of the species discussed are unusual because of the complete preservation of valve interiors which generally are not seen, though casts and molds are common.

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