This dataset contains length, width and weight measurements of <i>Echinotrix diadema</i> and <i>E. Calamaris</i> sampled in Mombasa Marine National Park (Kenya) from December 1994 to March 1995. Animals were collected collected at low tide in the reef lagoon and in the channel on the Northern side of Mombasa island, in front of the Kenya Marine Fishery and Research Institute (K.M.F.R.I.). Collection was done while snorkeling, no SCUBA was used. The data were digitized by VLIZ from the original report: Samyn, Y. (1995). Reproduction of two non-commercial sea urchins (Echinodermata: Echinoidea) in the Mombasa Marine National Park, Kenya. MSc Thesis. Vrije Universiteit Brussel: Brussel. 134 pp.