GLOSSARY. 409 



PETALOID. Shaped like the petal of a flower. 



PHACOPS (Gr. phake', 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. phragnia, 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 Pinnipedia. 

 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. platus, broad; keras, horn). A genus of Uni- 

 valve Molluscs. 

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



Crinoidea. 

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



the Quadrumana. 

 PLATYSOMUS (Gr. platus, 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. 

 PLTOSAURUS (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. 



