GLOSSARY. 409 



PETALOID. Shaped like the petal of a flower. 



PHACOPS (Gr. phakf, a lentil; ops, the eye). A genus of Trilo- 



bites. 

 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 possess- 

 ing 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 Pinfiipedia. 

 PINNULE (Lat. dim. of pinna). The lateral processes of the 



arms of Crinoids. 

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



the Fishes. 

 PLACOID (Gr. plax, a plate; eidos, form). Applied to the 



irregular bony plates, grains or spines which are found in the 



skin of various fishes (Elasmobranchii). 

 PLAGIOSTOMI (Gr. plagios, transverse; stoma, mouth). The 



Sharks and Rays, in which the mouth is transverse, and is 



placed on the under surface of the head. 



PLATYCERAS (Gr. plains, broad; keras, horn). A genus of Uni- 

 valve Molluscs. 

 PLATYCRINUS (Gr. plains, broad; krinon, lily). A genus of 



Crinoidea. 

 PLATYRHINA (Gr. plains, broad; rhines, nostrils). A group of 



the Quadrumana. 

 PLATYSOMUS (Gr. plains, wide; soma, body). A genus of Ganoid 



Fishes. 

 PLEISTOCENE (Gr. pleistos, most; kainos, new). Often used as 



synonymous with " Post-Pliocene. " 

 PLEUROTOMARIA (Gr. pleura, the side; tome", 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. 



