We describe a new genus of the chemosymbiotic bivalve family Vesicomyidae, Squiresica, for two Oligocene species, previously assigned to Archivesica, from western North America. Squiresica is characterized by a small and weakly inflated shell, a small to nearly absent pallial sinus, an Archivesica-like hinge dentition, with an indistinct to well incised lunular incision. Two species are assigned to this new genus: the type species, S. knapptonensis from western Washington State, USA, and S. marincovichi from Oligocene strata of Alaska, USA. Squiresica knapptonensis had previously been described from the upper Oligocene of the Lincoln Creek Formation; further specimens are here reported from a newly discovered seep deposit in the lower Oligocene part of the Lincoln Creek Formation.

Key words: Bivalvia, Vesicomyidae, cold-seep, deep-water, Oligocene, North America.

Frida Hybertsen [frida.hybertsen@nrm.se] and Steffen Kiel [steffen.kiel@nrm.se], Department of Palaeobiology, Swedish Museum of Natural History, Box 50007, 10405 Stockholm, Sweden. James L. Goedert [jamesgoedert@outlook.com], Burke Museum of Natural History and Culture, University of Washington, Seattle, Washington 98195, USA.