Lemuria

Were you looking for Lemuria, the province on  Groombridge-1830?

Lemuria was one of the six continents on the planet Arcadia, a UNSC colony in the Procyon system. It was abandoned after the Battle of Arcadia in 2531, and destroyed by the Covenant in the Fall of Arcadia in 2549.

Trivia
The continent was likely named in reference to Lemuria, a mythical lost continent on Earth.