GLOSSARY. 391 



Pletjrotomaeia (Gr. pleura, the side ; tomi, notch). A genus of Univalve 



shells. 

 Pliocene (Gr. pleion, more ; kainos, new). The later Tertiary period. 

 Pliopithecus (Gr. pleion, more ; pithekos, ape). An extinct genus of Monkeys. 

 Pliosaurus (Gr. pleion, more ; saura, lizard). A genus of Plesiosaurian 



Reptiles. 

 PoLYCYSTiNA (Gr. polus, many ; and kustis, a cyst). An order of Protozoa 



■with foraminated siliceous shells. 

 Polyp ART. The hard chitinous covering secreted by many of the Hydrozoa.. 

 Polype (Gr. polus, many ; ptous, foot). Restricted to the single individual of 



a simple Actinozo&n, such as a Sea-anemone, or to the separate zooids of a 



compound Actinozoon. Often applied indiscriminately to any of the Coelen- 



terata, or even to the Polyzoa. 

 PoLYPORA (Gr. polics, many; poros, a passage;. A genus of Lace-corals 



(Fenestellidce). 

 PoLYTHALAMOus (Gr. polus ; and tludamos, chamber). H aving many chambers ; 



applied to the shells of Foraminifera and Cephalopoda. 

 PoLYZOA (Gr. polus; and zoon, animal). A division of the Molluscoida com- 

 prising compoimd animals, such as the Sea-mat — sometimes called Bryozoa.. 

 PoRiFERA (Lat. poras, a pore ; and fero, I carry). Sometimes used to desig- 

 nate the Foraminifera, or the Sponges. 

 PR.a;M0LARS (Lat. prce, before ; molares, the grinders). The molar teeth of 



Mammals which succeed the molars of the milk-set of teeth. In man, the 



bicuspid teeth. 

 Proboscidea (Lat. proboscis, the snout). The order of Mammals comprising 



the Elephants. 

 Proccelous (Gr. pro, before ; koilos, hollow). Applied to vertebrae the bodies 



of which are hollow or concave in front. 

 Producta (Lat. jrroductibs, drawn out or extended). An extinct genus of 



Brachiopods, in which the shell is " eared," or has its lateral angles drawn 



out. 

 Protichnites (Gr. protos, first ; ichnos, footprint). Applied to certain im- 

 pressions in the Potsdam sandstone of North America, believed to have 



been produced by large Crustaceans. 

 Protophyta (Gr. protos ; and phicto^i, plant). The lowest division of plants. 

 Protoplasm (Gr. protos ; and plasso, I mould). The elementary basis of or- 

 ganised tissues. Sometimes used synonymously for the " sarcode " of the 



Protozoa. 

 Protorosaurus or Proterosaurus (Gr. protos, first ; orao, I see or discover ; 



saura, lizard : or proteros, earlier ; saura, lizard). A genus of Permian 



lizards. 

 Protozoa (Gr. protos; and zoon, animal). The lowest division of the animal 



kingdom. 

 PsAMMODUS (Gr. ^5a?>imo5„sand ; odous, tooth). An extinct genus of Cestra- 



ciont Sharks. 

 PSEUDOPODIA (Gr. psendos, falsity ; and i^ous, foot). The extensions of the 



body-substance which are put forth by the Rhizopoda at will, and which 



serve for locomotion and prehension. 

 PsiLOPHYTON (Gr. p)silos, bare ; phuton, plant). An extinct genus of Lyco- 



podiaceous plants. 

 Pteranodon (Gr. pteron, wing ; a, without ; odous, tooth). A genus of Ptero- 



saurian Reptiles. 

 Pteraspis (Gr. pterro^a, wing ; a^spis, shield). A genus of Ganoid Fishes. 

 Pterichthys (Gr. pteron, wing ; ichthus, fish). A genus of Ganoid Fishes. 

 Pterodactylus (Gr. pteron, wing ; d/xMulos, finger). A genus of Pterosaurian 



Reptiles. 

 Pteropoda (Gr. pAero^a, wing ; and pons, foot). A class of the Mollusca which 



swim by means of fins attached near the head. 

 Pterosaurli (Gr. pteron, wing ; saura, lizard). An extinct order of Reptiles. 

 Ptilodictya (Gr. ptilon, a feather ; diktuon, a net). An extinct genus of 



Polyzoa, 



