undet. Bivalvia

Geological context: Late Cretaceous, Fox Hills Fm, Trail City Mbr. Collection locality: Limopsis conc., conc 1, face and outcrops at 2 separate sites around S end of SSE-trending ridge at SW corner of Long's Ridge, and 7.3 mi W of Whitehorse, Dewey County, South Dakota, USA. Collected by Ian G. Speden, 1962. IP number 350760; lot count 1; taphonomy=concretion; accn=IPA.07048; associatedwith=on same slab: IP.350760,IP.350779,IP.350781,IP.350782,IP.350783,IP.350785,IP.350773,IP.350761,IP.350763,IP.350766,IP.350767,IP.350775,IP.350776,IP.350777,IP.350780,IP.350784,IP.350786,IP.350762,IP.350764,IP.350765,IP.350768,IP.350769,IP.350770,IP.350771,IP.350772,IP.350774,IP.350778.