Abstract Biometric data from the examination of skulls of Hippopotamus pentlandi Von Meyer (Canninita cave, Palermo, Sicily) are compared with the data relative to the skulls of two fossil hippos of european Pleistocene and of the living species Hippopotamus amphibius Linnaeus. Even taking into account the inhomogeneity of the fossil specimens and the deformation suffered by the skulls of H. pentlandi from Cannita cave, the examination confirms on one hand the stronger affinity of the sicilian species with the living H. amphibius and from the other hand the peculiarities that characterize this form with respect to the european continental ones. A comparative examination of the biometric characters of the skull of these latter species confirms the greater distance of H. antiquus Desmarest from the living species. It is stressed how the relations between the less bulky Pleistocene species (Hippopotamus incognitus Faure) with H. antiquus and with the living H. amphibius have not yet been completely clarified, owing both to the scantiness of the documentation and to the strong variability observed in the biometric characters of the few known skulls. It is noted how, in any case, this fossil form appears more similar to the living H. amphibius. For the moment its distinction at a specific level is accepted, even if with reservation, taking into account also the distinctive elements recognized in the post-cranial skeleton (FAURE, 1985), not examined here. Riassunto Vengono analizzati e posti a confronto i dati biometrici ricavati dall'analisi dei crani di Hippopotamus pentlandi Von Heyer della Grotta della Cannita (Palermo, Sicilia), degli ippopotami fossili del Pleistocene continentale europeo e della specie vivente Hippopotamus amphibius Linnaeus. Vengono da un lato confermate le maggiori affinità tra H. pentlandi ed H. amphibius vivente, nonché i caratteri peculiari che contraddistinguono la specie siciliana; dall'altro la più precisa caratterizzazione di H. antiquus Desmarest tra le forme fossili e le nette differenze che separano questa specie da H. amphibius vivente. La specie del Pleistocene europeo Hippopotamus incognitus Faure, viene accettata con riserva e viene fatta osservare l'affinità tra i caratteri cranici di questa forma fossile ed il viviente H. amphibius.