ABSTRACT: Abiometric study was carried out on planorbulinids occurring in eight samples from the upper Eocene-Lower Oligocene sediments of the Caltavuturo Formation cropping out at Portella Colla (Sicily, southern Italy). Counts and measurements on internal characters follow the methods currently employed for the similar genera Planorbulinella and Planolinderina such as the length of the initial spiral and the embryo size. The data obtained from the oriented thin sections allow to assign the late Eocene specimens to Planorbulina bronnimanni, whereas Oligocene specimens show larger embryonic apparatus, but the low amount of measured individuals prevents at present the definition of a new chronospecies. The well-known evolutionary trends of embryonic and nepionic accelerations, documented for the fossil Planorbulinella, seem not to be recognizable for Planorbulina.