The megalopae and juvenile crab stages of two species of Bythograea captured at 13 degree N, Bythograea thermydron and Bythograea microps have been comparatively studied. Comparison with one megalopa from Alvin collections at the Galapagos vents suggests that another species of Bythograea lives there. The "small" megalopae and most of the juvenile crabs cited by Williams in 1980 probably belongs to this new species, herein described as Bythograea intermedia sp. nov., which is presumably restricted to the Galapagos area, and whose size and morphological characteristics set it in an intermediate position between Bythograea thermydron and Bythograea microps .