The Barolians were a species known of in the 24th century. They have loose, gray skin, blue eyes set into their skulls, and noses that spread from ear to ear.
In 2364, Senator Pardek attended a Barolian trade conference. (TNG episode: "Unification")
In 2368, a Barolian freighter was used to transport stolen goods for the Romulans. (TNG episode: "Unification")
In 2379, Captain Jean-Luc Picard, "Pug" Joseph, Carter Greyhorse, and Decalon were disguised as Barolians when they infiltrated Kevratas. (TNG novel: Death in Winter)
Presumably, the bulk of the Barolian population was wiped out by the Borg when Barolia was cleansed of all life in 2381. (TNG novel: Greater Than the Sum)