A new medusoid hydrozoan,
Plectodiscus malayitesn. sp., belonging to the Family Velellidae is described from Carboniferous rocks of the Malay Peninsula. They are preserved as flattened internal float structures or pneumatophores and are the first examples from this part of the world. In contrast to other occurrences, the great abundance of these sailed organisms suggests that, like extant species of Velella, these organisms were an important component of the pelagic fauna and were at least locally abundant in open seas of the late Paleozoic.