PALAEOTHERIDAE. (Gr. palaios, ancient; ther, beast).  A group of Tertiary Ungulates.

PALAEOZOIC (Gr. palaios, ancient; and zoe, life).  Applied to the oldest of the great geological epochs.

PARADOXIDES (Lat. paradoxus, marvellous).  A genus of Trilobites.

PATAGIUM (Lat. the border of a dress).  Applied to the expansion of the integument by which Bats, Flying Squirrels, and other animals support themselves in the air.

PECOPTERIS (Gr. peko, I comb; pteris, a fern).  An extinct genus of Ferns.

PECTEN (Lat. a comb).  The genus of Bivalve Molluscs comprising the Scallops.

PECTORAL (Lat. pectus, chest).  Connected with, or placed upon, the chest.

PENTACRINUS (Gr. penta, five; krinon, lily).  A genus of Crinoids in which the column is five-sided.

PENTAMERUS (Gr. penta, five; meros, part).  An extinct genus of Brachiopods.

PENTREMITES (Gr. penta, five; trema, aperture).  A genus of Blastoidea, so named in allusion to the apertures at the summit of the calyx.

PERENNIBRANCHIATA (Lat. perennis, perpetual; Gr. bragchia, gill).  Applied to those Amphibia in which the gills are permanently retained throughout life.

PERISSODACTYLA (Gr. perissos, uneven; daktulos, finger).  Applied to those Hoofed Quadrupeds (Ungulata) in which the feet have an uneven number of toes.

PETALOID.  Shaped like the petal of a flower.

PHACOPS (Gr. phake, a lentil; ops, the eye).  A genus of
Trilobites.

PHALANGES (Gr. phalanx, a row).  The small bones composing the digits of the higher Vertebrata.  Normally each digit has three phalanges.

PHANEROGAMS (Gr. phaneros, visible; gamos, marriage).  Plants which have the organs of reproduction conspicuous, and which bear true flowers.

PHARYNGOBRANCHII (Gr. pharugx, pharynx; bragchia, gill).  The order of Fishes comprising only the Lancelet.

PHASCOLOTHERIUM (Gr. phaskolos, a pouch; therion, a beast).  A genus of Oolitic Mammals.

PHRAGMACONE (Gr. phragma, a partition; and konos, a cone).  The chambered portion of the internal shell of a Belemnite.

PHYLLOPODA (Gr. phullon, leaf; and pous, foot).  An order of Crustacea.

PINNATE (Lat. pinna, a feather).  Feather-shaped; or possessing lateral processes.

PINNIGRADA (Lat. pinna, a feather; gradior, I walk).  The group of Carnivora, comprising the Seals and Walruses, adapted for an aquatic life.  Often called Pinnipedia.

PINNULAE. (Lat. dim. of pinna).  The lateral processes of the arms of Crinoids.

PISCES (Lat. piscis, a fish).  The class of Vertebrates comprising the Fishes.