Twenty species of bivalves are described from the Ixtaltepec Formation, in Nochixtlan, Mexico. Representatives of the genera Parallelodon, Myalinella, ptimyalina, Leptodesma, Pterinopectinella, Aviculopecten, Limipecten, Streblopteria, Euchondria, Schizodus, Permophorus, Astartella, Edmondia, and Ectogrammysia are present. These species, and those of nuculoid bivalves previously described from the same formation, include infaunal and epifaunal forms that lived in shallow marine environments from Morrowan to Desmoinesian ages. Pennsylvanian bivalves from Nochixtlan are related to the Midcontinent and Appalachian faunas, which indicate that there was an oceanic connection between these areas in a latitudinal belt near the equator that partially covered southeastern Mexico.

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