386 GLOSSARY. 



PALAEONTOLOGY, the science which treats of fossil remains. 

 PENTREMITES, a genus of fossils related to the star-fishes. 

 PHILLIPSIA, a genus of trilobites. 

 PINNA, a genus of bivalve shells. 

 PLATYCRINUS, a genus of fossil crinoids. 

 PLEUROTOMARIA, a genus of fossil univalve shells. 

 POLYZOA, a low class of mollusks. 

 PRODUCTUS, a genus of bivalve shells. 



PROTOZOANS, an indistinctly defined branch of the animal kingdom, inclu- 

 ding the lowest forms. 

 PSAMMODUS, a genus of fossil fishes. 

 PTEROPODA, a class of swimming mollusks. 



QUARTZITE, metamorphic sandstone. 



RECEPTACULITES, a fossil coral-like body, probably foraminiferous. 

 RETZIA, a genus of bivalve shells. 

 RHODOCRINUS, a genus of fossil crinoids. 

 RHYNCHONELLA, a genus of bivalve shells. 



SANDALODUS, a genus of fossil fishes. 



SELACHIANS, an order of fishes including the sharks and others. 



SEPTARIA, argillaceous stony masses, traversed in different directions by 



veins of purer mineral substance ; usually lenticular in form and probably 



called " petrified turtles." 

 SHAFT, a perpendicular way into & mine. 

 SMITHIA, a genus of fossil corals. 

 SPIRIFER, a genus of fossil bivalve shells. 

 STRATUM, (plural, strata), a layer or bed as applied in geology. 

 STROPHODONTA, a genus of fossil bivalve shells. 



SYNCLINAL AXIS, a given line toicard which strata dip in both directions. 

 SYRINGOPORA, a genus of fossil corals. 



TRILOBITE, a family of fossil crustaceans related to the horse-foot crab. 

 TUFA, calcareous, stony masses, usually very porous, formed by deposition 

 from water of springs holding carbonate of lime in solution. 



WALDHEIMIA, a genus of fossil bivalve shells. 



ZAPHRENTIS. a genus of fossil corals. 



