Citron
There are also a number of citron hybrids; for example, ponderosa lemon, the lumia and rhobs el Arsa are known citron hybrids, some are claiming that even the Florentine citron is not pure citron, but a citron hybrid.
Siracusa Lemon
The Siracusa lemon (in Italian, "Limone di Siracusa IGP") is the fruit of the cultivar "femminello siracusa" and its clones, corresponding to the botanical species Citrus x limon L. Burm. The "femminello siracusano" cultivar is the most common variety of lemon in Italy, with the Province of Syracuse (Siracusa) region accounting for 42% of the national lemon-growing land area.