Two new species of Carcinonemertes are described from leucosiid crabs found in the northeast and southwest Pacific Ocean. Carcinonemertes kurisi sp. nov. is associated with Randallia ornata, a crab commonly found from northern California to Baja California, Mexico. Carcinonemertes tasmanica sp. nov. is associated with Dittosa laevis, a crab found on mudflats in Hobart, off Tasmania, Australia. These are the first descriptions of Carcinonemertes recorded from leucosiid hosts. The two new species are compared with each other and other species in the genus Carcinonemertes. Diagnostic features of both species include a short stylet and a unique, corkscrew-shaped sheath. Notes and comparisons on measurements, functional morphology, distribution on host, and behaviour were obtained by examining live worms and preserved specimens.
