Resumo. Only six out of a total of 25 genera of Pirenidae have been recorded from the New World. Here we report the presence of a seventh genus, Watshamia (subfamily Pireninae), and describe Watshamia sasa Hanson & Jansen-González, sp. nov. from Costa Rica This finding suggests that additional genera of Pirenidae may eventually be found in the Neotropics and that in attempting to identify genera of poorly studied taxa, Old World genera should not be discounted. A brief discussion is provided of characters used to separate Pireninae from Tridyminae, as well as an updated summary of the biology of Pirenidae.