Nephrolepidina praemarginata (Douvillé, 1908) from Majella Mt. (Central Apennines).

Two Nephrolepidina populations (E77’, n=54; E76J, n=9) from Santa Croce near Caramanico were biometrically investigated. For each sample we considered three parameters and three factors and their mean values. According to De Mulder (1975), the factor Ai (degree of enclosure of the deuteroconch on the protoconch) and the parameter C (number of adauxiliary chambers) suggest that the populations belong to N. praemarginata (Douvillé, 1908). The mean sizes of the protoconch and the deuteroconch are significantly larger than other known populations. This is interpreted as due to environmental factors. According to recent studies on symbiont bearing nummulitids by Pechéux (1995) the diameter of the embryonic chambers increases downslope up to the ecological optimum and than decreases again. Hottinger (1997) suggested that orbitoidiforms such as Nephrolepidina may have had symbionts living in the lateral chamberlets as in the present-day Baculogypsinoides. Downslope transport mixing specimens from different populations along the depth gradient is apparently widespread, thus minimizing the effect of specimens from the ecological optimum zone, which in turn validates the well-known biometrical trends in Nephrolepidina