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Abstract
Morphological characters common to the Prosomatifera, but previously not reported within the Operculatifera, favor the erection of three new genera and the establishment of two new subfamilies within the Operculatifera. Ordochitina gen. nov. has spines and/or ridges distributed in longitudinal rows. Orbichitina gen. nov. is characterized by spines arranged in a basal ring. Cutichitina gen. nov. has an outer layer clearly detached from the vesicle wall to form a sleeve. The proposal of the Subfamily Orbichitininae subfam. nov. is based on the presence of basal processes, and that of the Subfamily Cutichitininae subfam. nov. on the presence of a sleeve around the vesicle. These characteristics, newly reported in the Operculatifera, have implications on the classification of Prosomatifera. The Subfamily Eremochitininae is emended and now restricted to forms having an outer layer only extending aborally beyond the base. Two new subfamilies, (Velatachitininae subfam. nov. and Pellichitininae subfam. nov.) are proposed for Conochitinidae and Lagenochitinidae characterized by an outer layer clearly separated from the wall of the chamber. A new genus (Pellichitina gen. nov.) also is erected.