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 Ccelen- 

 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). Having many chambers ; 

 applied to the shells of Foraminifera and C'epJialopoda. 



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

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



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

 nate the Foraminifera, or the Sponges. 



PRJBMOLABS (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. 



PROCCKLOUS (Gr. -f.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 ; iehnos, 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 plusso, I mould). The elementary basis of or- 

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



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. 

 PSAMMOHUS (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. 



PTKRASPIS (Gr. pteron, wing ; aspis, shield). A genus of Ganoid Fishes. 

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

 PTERODACTYLDS (Gr. pteron, wing ; daktulos, linger). A genus of Pterosaurian 



Reptiles. 

 PTEROPOUA (Gr. pteron, wing ; and pous, foot). A class of the Mollu-sca which 



swim by means of tins 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. 



