Lewis & Short

Tartessus (Tartēsus), or -os, i, f., a very ancient maritime town of Spain, now El Rocadillo, near S. Roque, Mel. 2, 6, 9; Plin. 3, 1, 3, § 7; Sil. 3, 399; 5, 399.
Hence,

  1. A. Tartessĭus (Tartēsĭus), a, um, adj., of or belonging to Tartessus, Tartessian: litora, Ov. M. 14, 416: stagna, Sil. 10, 538: muraena, Varr. ap. Gell. 7, 16, 5.
    Poet. for Spanish: tellus, Sil. 13, 673; 15, 5.
    Subst.: Tartessĭi, ōrum, plur., the inhabitants of Tartessus, Plin. 7, 48, 49, § 154.
  2. B. Tartessĭăcus (Tartēsĭăcus), a, um, adj., Tartessian: aequor, Sil. 6, 1: thyrsi, i. e. lettuce, Col. 10, 370.
    Poet. for Spanish: harenae, Claud. in Ruf. 1, 101: Iberus, Sid. Carm. 5, 286.
  3. C. Tartessis (Tartēsis), ĭdis, adj. f., Tartessian: lactuca, Col. 10, 192.