A class M planet inhabited by proto-hominids, which Professor Galen had visited shortly before his death and which gave Picard an early clue to the ancient genetic puzzle.
Ruah IV appears in the Next Generation episode The Chase. After Richard Galen dies of wounds received in a Yridian attack on his shuttle, Picard retraces his old mentor's recent travels and finds that he had been here and was next bound for Indri VIII.
The planet seems to offer nothing an archaeologist would want. It has abundant animal life and a species of early hominid, but no ruins and no trace of any past civilisation.
That absence is itself the clue. Galen had been collecting samples of living DNA, not artefacts, and the fragments from many worlds fit together as a programme left by the first humanoids. The Enterprise goes on to Indri VIII, only to find its biosphere burned away by a rival searcher.