Deep‐water Calappidae collected by German and Russian expeditions to the western Indian Ocean and additional material from several European and American museums were studied. Calappa japonica Ortmann, 1892 was recorded from the Red Sea for the first time, where it occurs in unusually deep waters and C. pustulosa Alcock, 1896 was recorded for the first time off Madagascar. Eight species of Mursia Desmarest, 1823 are known from the Indian Ocean (M. africana Galil, 1993, M. aspera Alcock, 1899, M. bicristimana Alcock and Anderson, 1894, M. coseli Crosnier, 1997, M. cristiata H. Milne Edwards, 1837, M. flamma Galil, 1993, M. curtispina Miers, 1886, and M. minuta n. sp.). For M. bicristimana the status was clarified and a new species described. This description is partly based on a specimen which prior to this study had been erroneously considered a syntype of M. bicristimana. New characters and a key are provided to facilitate identification of the Indian Ocean species of Mursia. The contrasting geographic di...