The first species of Prionalpheus from the eastern Pacific, and new records of caridean shrimp (Crustacea: Decapoda: Caridea) from the western coast of Mexico

Four species of shallow water caridean shrimp new to the Mexican fauna are reported. The specimens were collected along the coast of the state of Nayarit and at Isla Isabel Mexico. Prionalpheus nayaritae, new species, represents the first occurrence of this rare genus in the eastern Pacific. The new species can be recognized by the presence of asymmetrical mandibles, a characteristic of Prionalpheus. Three other new records extend the previous known distributions from Panama (Alpheus firmus), Colombia (Synalpheus bannerorum), and Hawaii and Clipperton Island (Processa hawaiensis), to continental Mexico. Morphological differences with specimens used in previous descriptions or reports are provided.