Abstract
While reviewing the Glycymerididae of the Panamic Province we encountered an unusual species of Tucetona Iredale, 1931, in the Gulf of California, Mexico. After examining type and related specimens at museums in the USA and UK, we have determined thespecies is new to science. It is herein named Tucetona isabellae. In our description we use morphological characteristics outlined in Tschudin (2001) and Squires (2010).