Morphostructure and systematics of Linderina brugesi Schlumberger, 1893 (Foraminifera, eocene)

The morphostructure of the genus Linderina SCHLUMBERGER, 1893 is revised re lying on a structural study of the type species L. bruguesi, SCHLUMBERGER. Its test is lamellar-involute, with annular-cyclic growth of orbitoidal typ e. It has only one kind of stolons which are crosswise-oblique, alternately arranged in axial rows, and correspond with the apertures in the last cham ber. The lateral thickenings of the test are formed by the superposition of the successive involute outer lamellae of the different chambers, lacking piles and granules, and the irregularity of the lateral surfaces is due to the lateral rounded reliefs of the alternate chamberlets. The embryonic app aratus is quadrilocular, with three subspherical initial chambers forming a triconch, and a fourth larger, arcuate chamber with rows of apertures in b oth sides from which the orbitoidal growth starts. An explanation is given for the morphogenesis of embryos in triconch, observed in a number of foram iniferal genera. L. brugesi shows a close similarity to American Eocene spe cies Caudriella ospinae (CAUNDRI), which differs from Linderina in that it has lateral chamberlets. Because of this affinity, Caudriella is included i n the Linderinidae. A redefinition of the genus Linderina and of the family Linderinidae is performed. The genera Eoannularia and Epiannularia, previo usly classified into the Linderinidae, do not fit into the new characteriza tion of the family and are thus grouped into a new family, named Eoannulari dae.