Morum clatratum n. sp. and Morum roseum n. sp. are described from depths of 100-200 m in the Marquesas Islands. Mode of development inferred from protoconch morphology and comparison with the protoconchs of Harpa with teleplanic larvae suggests that the new species have planktotrophic larval development, and that they are expected to range widely outside the Marquesas. In addition, Morum kurzi, M. macdonaldi, and M. teramachii, with inferred planktotrophic development, and M. watanabei, with inferred non-planktotrophic development, are newly recorded from South Pacfic localities. The distribution of individual species of Morum appears to reflect dispersal during the planktonic phase, rather than movement of the lithospheric plates on the geological scale. The Caribbean Morum oniscus and M. lamarckii, respectively with inferred non-planktotrophic and planktotrophic development, are treated as separate valid species.