Three new species ofLoxosomaare described,L. nungandL. song, on the polychaetePectinaria brevispinisfrom the reef flat in front of Phuket Marine Biological Center, andL. sumon the polychaeteAxiothella obockiensisfrom a sand flat at Nai Yang Beach, Phuket Island. The genusLoxosomais briefly reviewed. Species originally referred toLoxosomabut now transferred toLoxosomellaare listed; insufficiently characterized species probably belonging toLoxosomellaare listed as well. The monospecific genusLoxostemmais synonymized withLoxosoma. The subgenus nameLoxosominais proposed to replace the junior homonymLoxomorpha.