A NEW SPECIES OF SOMALINA (SOMALINA-HOTTINGERI) WITH PARTIALLY VACUOLATE LATERAL WALLS FROM THE MIDDLE EOCENE OF OMAN

Somalina hottingeri, a new species with partially vacuolate lateral wa lls is described from the Middle Eocene of Oman. It is distinguished f rom the only previously recorded species with this wall structure (S. transitorius (Hottinger)) by having equatorial chambers that are relat ively low throughout the test. On the basis of this character, it is s uggested that S. hottingeri evolved from the Opertorbitolites douville i Group (redefined here) and that it gave rise to the true somalines. S. transitorius is regarded as arising from O. latimarginalis (ex. O. latimarginalis Group, introduced in this study) but not to have given rise to any other species. Since forms of Somalina with only partially vacuolate walls appear to be confined to the late Early Eocene to ear ly Middle Eocene, it is concluded that the presence of this wall struc ture provides a useful stratigraphic marker.