Federation member species recognizable by their large, round heads, with a representative on the Federation Council in the late 23rd century.
Arcadians are humanoids with large, round, doll-like heads, with hair on either side and none on top. Little else about their biology, culture or homeworld has been revealed on screen.
An Arcadian sat on the Federation Council in Star Trek IV: The Voyage Home, present as the Klingon ambassador demanded Kirk's extradition and as an alien probe threatened Earth. Their seat on the Council makes them one of the many member species represented in Federation government.