Orbitoidids—foraminifers with large typically disk-shaped tests.
Ordovician—second oldest [period] of the [Paleozoic] era; follows the [Cambrian], precedes the [Silurian].
Ossicle—loosely used as a small plate.
Paleocene—oldest epoch of the [Tertiary] [period]; precedes the [Eocene].
Paleozoic—that era of geologic time that follows [Precambrian] time and precedes the [Mesozoic] era.
Pedicle opening (pedicle [foramen])—see [Foramen].
Pelecypod—a bivalved aquatic invertebrate; member of class Pelecypoda, [phylum] Mollusca.
Pennsylvanian—the sixth oldest [period] of the [Paleozoic] era; follows the [Mississippian], precedes the [Permian].
Period—a division of geologic time ([Pl. 1]).
Periostracum—the horny outer covering or epidermis on shells.