GLOSSARY. 391 



PLEUROTOMARIA (Gr. pleura, the side ; tomt, 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. 



POLYPARY. The hard chitinous covering secreted by many of the Hydrozoa. 

 POLYPE (Gr. polus, many ; pous, foot). Restricted to the single individual of 



a simple Actinozoon, 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. polus, many; poros, a passage). A genus of Lace-corals 



(Fenestellidce}. 

 POLYTHALAMOUS (Gr. polus ; and thalamos, chamber). H aving many chambers ; 



applied to the shells of Foraminifcra and Cephalopoda. 



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

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

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

 nate the Foramini/era, or the Sponges. 

 PR^MOLARS (Lat. prce, before ; molar es, 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. j.ro, before ; koilps, hollow). Applied to vertebrae the bodies 



of which are hollow or concave in front. 

 PRODUCTA (Lat. productus, 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 phuton, 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, h'rst ; 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. psammos, sand ; odous, tooth). An extinct genus of Cestra- 



ciont Sharks. 

 PSEUDOPODIA (Gr. pseudos, falsity ; and pous, 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. psilos, 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. pteron, wing ; aspis, shield). A genus of Ganoid Fishes. 

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

 PTERODACTYLUS (Gr. pteron, wing ; daktulos, finger). A genus of Pterosaurian 



Reptiles. 

 PTEROPODA (Gr. pteron, wing ; and pous, foot). A class of the Mollusca which 



swim by means of fins attached near the head. 



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

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



Polyzoa. 



