The western group, corresponding with the ancient Pityusae or Pine Islands, also comprises two relatively large islands, Iviza (Spanish, Ibiza or, formerly, Ivica) and Formentera, with the islets of Ahorcados, Conejera, Pou and Espalmador.
Formentera is described with Iviza.
The Ophiusa of the Greeks (Colubraria of the Romans) is now known as Formentera.
The two left Paris in 1806 and began operations among the mountains of Spain, but Biot returned to Paris after they had determined the latitude of Formentera, the southernmost point to which they were to carry the survey, leaving Arago to make the geodetical connexion of Majorca with Ivica and with Formentera.