We describe a new species of remipede crustacean from an anchialine cave system in the Exuma Cays, Bahamas. Pleomothra fragilis n. sp. is the second species assigned to the genus Pleomothra Yager, 1989. It is a relatively small species that occurs in sympatry with other remipedes, copepods, ostracods and amphipods. Pleomothra fragilis can easily be distinguished from Pleomothra apletocheles by the shape of its head shield, relatively long caudal rami, differently shaped, smaller maxillules, and a completely reduced lacinia mobilis on the left mandible. The reduction of the left lacinia and the sixth maxillular segment represent unique features that are only found in Pleomothra. At present, interpretations of these reductions are purely speculative since developmental data of remipedes are largely lacking. However, our recent collection of five larvae included a postnauplius that could be identified as belonging to the genus Pleomothra. The postnauplius exhibits transitional morphologic features that facilitate to evaluate autapomorphies in Pleomothra.