594 GLOSSARY. 



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



which a "float" is present. 

 PHYSOPHORID^ (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, 1 eat). Plant-eating, or 



herbivorous. 

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



s>Aocoa 



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



vora 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. 

 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 skin of various fishes (Elas- 



mobranchii). 

 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. 



PLANAEIDA (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 the Hy- 

 drozoa. 



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

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



division of Scolecida comprising the Tapeworms, &c. 



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

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



breathinsr Vertebrates. 



PLEURON (Gr. pletiron, 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 kustis, cyst). The air-sac or float of 



certain of the Oceanic Hydrozoa (Physophoridce). 

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



dilatation of the coenosarc in the Physophoridce which surrounds the 



pneumatocyst. 

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



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

 PODOPHTHALMATA (Gr. pous, foot ; 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 ; pliago, 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. polus, 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 zob'ids of a 

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

 teraia, or even to the Polyzoa. 



