GLOSSARY. 675 



Applied formerly to the Physophoridce, an order of Oceanic Hydrozoa, in 



which a " float " is present. 

 PHYSOPHORID^E (Gr. phusa, air-bladder ; and phero, I carry). An order of 



Oceanic Hydrozoa. 



PHYTOID (Gr. phuton, a plant ; and eidos, form). Plant-like. 

 PHYTOPHAGOUS (Gr. phuton, a plant ; and phago, I eat). Plant-eating, or 



herbivorous. 



PINNATE (Lat. pinna, a feather). Feather-shaped, or possessing lateral pro- 

 cesses. 

 PINNIGRADA (Lat. pinna, a feather; gradior, I walk). The group of Carni- 



vora, com prising the Seals and Walruses, adapted for an aquatic life. Often 



called Pinnipedia. 



PINNULE (Lat. dim. of pinna}. The lateral processes of the arms of Grinoids. 

 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 foetus. 



PLACENTAL. Possessing a placenta, or connected with the placenta. 

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



plates, grains, or spines which are found in the skim of various fishes 



(Elasmobranchii). 

 PLAGIOSTOMI (Gr. pfaaios, transverse ; stoma, mouth). The Sharks and Ptays, 



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



head. 



PLANARIDA (Gr. plane, wandering). A sub-order of the Turbellaria. 

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



the sole of the foot to the ground in walking. 

 PLANULA (Lat. 'planus, flat). The oval ciliated embryo of certain of ttie 



Hydrozoa. 



PLASTRON. The lower or ventral portion of the bony case of the GJhelonians-. 

 PLATYELMIA (Gr. platus, broad ; and helmins, an intestinal worm). The 



division of Scolecida comprising the Tape-worms, &c. 



PLATYRHINA (Gr. platus, broad ; rhines,xiostrils). A group of the Quadrumana. 

 PLEURA (Gr. the side). The serous membrane covering the lung in the air- 

 breathing Vertebrates. 



PLEURON (Gr. pleuron, a rib). The lateral extensions of the shell of Crustacea. 

 PLUTEUS (Lat. a pent-house). The larval form of the Echinoidea. . 

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

 PNEUMATOCYST (Gr. pneuma, air; and: kusfis, cyst). The air-sac or float of 



certain of the Oceanic Hydrozoa (Physophoridce). 

 PNEUMATOPHORE (Gr. pneuma, air ; and phero, I carry). The proximal 



dilatation of the coenosarc in the Physophoridce which surrounds the pneu- 



matocyst. 

 PNEUMOSKELETON (Gr. pneuma; and skeletos, dry). The hard structures 



which are connected with the breathing organs (e.g., the shell of Molluscs). 

 PODOPHTHALMATA (Gr. pous, f oot ; and ophthalmos, eye). The division of 



Crustacea in which the eyes are borne at the end of long foot-stalks. 

 PODOSOMATA (Gr. pous, foot ; soma, body). An order of ' Arachnida. 

 POEPHAGA (Gr. poe, grass ; phago, I eat). A group of the Marsupials. 

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



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

 POLYCYSTINA (Gr. po'us, many ; and kustis, a cyst). An order of Protozoa, 



with foraminated siliceous shells. 

 POLYGASTRICA (Gr. polus ; and gaster, stomach). The name applied by 



Ehrenberg to the Infusoria, under the belief that' they possessed many 



stomachs. 



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- 



lerata, or even to the Polyzoa. 



