Two new species of the formerly monotypic gobiesocid genus Discotrema are described. Discotrema monogrammum is described from specimens collected from crinoids in Papua New Guinea and Indonesia, with photographic and literature records from the Great Barrier Reef, Philippines, and Christmas Island, Indian Ocean. The specimens were first believed to be a color form of D. crinophilum, described from Fiji and Papua New Guinea, and also commensal in crinoids. Both species have a single, white or pale yellow lateral stripe, whereas D. crinophilum also has a mid-dorsal white stripe; unique mitochondrial DNA sequences showed that D. crinophilum and D. monogrammum are distinct lineages. Discotrema zonatum, which has irregular dark bars on the side of the body, is described from a single specimen from Fiji, apparently commensal on soft coral. The three species are also distinguished by pectoral-fin ray counts and three proportional measurements. Some authors have placed Lepadichthys lineatus in the genus Discotrema, but its disc morphology and other characters indicate that it should remain in Lepadichthys. A key to the species of Discotrema is provided.