Abstract
A new genus and two new species of Bathynellacea are described from California in USA. Califobathynella, a new genus, belongs to the subfamily Leptobathynellinae, and is closely related to the genera Parvulobathynella and Leptobathynella but differs from them with respect to labrum, maxillule, maxilla, and male thoracopod VIII. Based on the detailed structure of mouthparts, the phylogenetic relationship of three genera are discussed. The phlogenetic age of the stem species of three genera are estimated at the late Jurassic, based on their phylogenetic relationship and distribution pattern. Two new species, C. noodti and C. teucherti differ from each other in the structure of labrum.