Carinoma hamanako sp. nov., the ninth member of the genus, is described based on three specimens collected in Lake Hamana, Shizuoka Prefecture, Pacific coast of Honshu, Japan. The new species can be distinguished from its congeners by the blind-ending rhynchocoelic villar vessels, the lateral rhynchocoel vessels rejoining the lateral vessels, the unbranched excretory canals, the situation of the posterior part of the mid-dorsal nerve within the longitudinal muscle layer of the body wall, and the absence of a vascular plexus in the foregut region. A phylogenetic analysis based on the nuclear 28S rRNA and mitochondrial cytochrome c oxidase subunit I genes shows that C. hamanako sp. nov. forms a clade with two congeners, C. mutabile Griffin, 1898 and C. tremaphoros Thompson, 1900, thus supporting the generic placement of the new species.