498 GLOSSARY. 



Pinnule (Lat. dim. of pinna). The lateral processes of the arms of Crinoicls. 



Pisces (Lat. piscis, a fish). The class of Vertebrates comprising the Fishes. 



Placenta (Lat. a cake). The "after-birth," or the organ by which a vascu- 

 lar connection is established in the higher Mammalia between the mother 

 and the fcetus. 



Placental. Possessing a placenta ; or connected with the placenta. 



Placoid (Gr. plax, a plate ; cidos, form). Applied to the irregular bony plates, 

 grains, or spines which are found in the skin of various fishes {Elasmo- 

 branchii). 



Plagiostomi (Gr. plagios, transverse ; stoma, mouth). The Sharks and Eays, 

 in which the mouth is transverse, and is placed on the under surface of the 

 head. 



Plantigrade (Lat. planta, the sole of the foot ; gradior, I walk). Applying 

 the sole of the foot to the ground in walking. 



Plastron. The lower or ventral portion of the bony case of the Chelonians. 



Platyrhina (Gr. platus, broad; rhincs, nostrils). A group of the Quadrumana. 



Pleistocene (Gr. plcistos, most ; kainos, new). Often used as synonymous 

 with "Post-Pliocene." 



Pleurodont (Gr. pleuron, rib, side ; odous, tooth). Having the teeth anchy- 

 losed with the inner side of the jaws. 



Pleuron (Gr. pMiron, a rib). The lateral extensions of the shell of Crustacea. 



Pneumatic (Gr. pneuma, air). Filled with air. 



Podophthalmata (Gr. poics, foot ; and ophthalmos, eye). The division of 

 Cmstacea in which the eyes are borne at the end of long footstalks. 



PoLLEX (Lat. the thumb). The innermost of the five normal digits of the 

 anterior limb of the higher Vertebrates. In man, the thumb. 



Poltcystina (Gr. polus, many ; and hustis, 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 ; jmios, foot). Restricted to the single individual of 

 a simple Adinozoon, such as a Sea-anemone, or to the separate zooids of a 

 compound Adinozoon. Often applied indiscriminately to any of the Ccelen- 

 terata, or even to the Polyzoa. 



Polypide. The separate zooid of a Polyzoon. 



Polypidom. The dermal system of a colony of a Hydrozoon, or Pohjzoon. 



PoLYPiTE. The separate zooid of a Hydrozoon. 



Polythalamous (Gr. polus ; and thalamos, chamber). Having many cham- 

 bers ; applied to the shells of Foraminifera and Cephalopoda. 



Polyzoa (Gr. polus; and zo6ii, animal). A division of the Molluscoida com- 

 prising compound animals such as the Sea-mat — sometimes called 

 Bryozoa. 



PoLYZOARiUM. The dermal system of the colony of a Polyzoon (= Polypidom). 



Porcellanous. Of the texture of porcelain. 



PoRiFERA (LaX.ponis, a pore ; and /ero, I carry). Sometimes used to designate 

 the Foraminifera, or the Sponges. 



Post-anal. Situated behind the anus. 



PosT-CESOPHAGEAL. Situated behind the gullet. 



Post-oral. Situated behind the mouth. 



Pr^maxill^ — see Intermaxillse. 



Premolars (Lat. prce, before ; molares, the grinders). The molar teeth of 



