Vörös A. szerk.: Fragmenta Mineralogica Et Palaentologica 14. 1989. (Budapest, 1989)
Islands, California, the Caribbean Region, the Red Sea, the Persian Gulf, and S of the Comorin Cape in the Indian Ocean (Fig. 5). Data for Nummulites cummingi come from one island of the Maldives. Nummulites occur here on one of the external slopes of a coral reef and in its lagoon. At the external slope, at a depth of 40- 70 m, they represent 5-30% of the fauna. Within the depth range of 60- 70 m, this rate reaches 30%. In the lagoon, at a depth of 40- 50 m, frequency of Num mulites cummingi ranges between 5-20% within the fauna. Frequency is decreasing in accordance with depth. One of the most intensively and comprehensively examined nummulitid is Operculina ammonoides. Its data are taken from localities in the Red Sea. Here the species occurs at depths of 15-50 m at a wide range with areal distribution. In the Indian Ocean (Maldives) this species makes up only 10-20% of the fauna at a depth of 60 m on the external slope of the reef. In the lagoon, mostly at a depth interval of 30-40 m, the area of this fauna can be found where the frequency ranges between 20-90 %. Heterostegina depressa is the most frequently studied recent larger Foraminifera. It has been examined not only in its natural habitat but in the laboratory as well. Its skeleton^ cell structure and biology are well-known (RÖTTGER 1972, 1973, 1976, 1978, SCHMALJOHANN and RÖTTGER 1976). Its depth range in the Red Sea is 30-70 m, in the IndianOcean 20- 70 m, and at Hawaii, near Oahu it is 10-70 m. Occurrences in the Indian Ocean are also accompanied by data referring to frequency. Here, at the external slope the species exists at a depth of 20-70 m: at 20 m it is 40 % of the fauna; of 35 m it reaches the maximum frequency (85%), and then following a significant sudden decrease, at 70 m it reaches again the 75% value. The ecological requirements for the existence of Amphisteginae are also well-known (HANSEN 1972, ZMIRI et al. 1974, LARSEN 1976;, REISS 1977, HALLOCK 1979, 1980, 1981). Their depth range in the Red Sea is between 10-150 m. Their frequency reaches the maximum of 35% at 90 m, and at a depth of 50 m their rate is 15%. Based upon the data above we can conclude that the four most important recent taxa of larger Foraminifera (in certain cases their rate can be put to 45-50 % of the total fauna) exist at a depth of 18-90 m, and according to their percentage, their optimum environment may , be put to a depth of 20-40 m. Morphologically these taxa belong to two different groups of fundamental importance. N. cummingi and Amphistegina lessoni have a convex, spherical shell type, while OperD4AOFUMMATIC MODEL culina ammonoides and Heterostegi na depressa have a flat shell type. Borelis with sporadic data belongs to the first, while Sorites , Amphisorus and Calcarina to the second group. The depth range model for the larger Foraminifera, based on the data above is the following (Fig. 6). Fig. 6 A model for bathymétrie relations of the Eocene sea in the SW Transdanubian Central Range
