344 GLOSSARY. 



vascular connection is established in the higher Mammalia between the 



mother and the foetus. 



PLA-CEN'TAL. Possessing a placenta, or connected with the placenta. 

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



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



(MasmobrancMi). 

 PLA-GI-OS'TO-MI (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. 



PLA-NAB'I-DA (Gr. plane, wandering). A sub-order of the TurbeUaria. 

 PLAN-TI-GBA'DA. 

 PLANT' I-GBADE (Lat. planta, the sole of the foot ; gradior, I walk). Applying 



the sole of the foot to the ground in walking. 

 PLAN'U-LA (Lat. planus, flat). The oval ciliated embryo of certain of the Hy- 



drozoa. 



PLAS'TRON. The lower or ventral portion of the bony case of the Chelonians. 

 PLAT-Y-EL'MI-A (Gr. platus, broad ; and kelmins, an intestinal worm). The 



division of Scolecida comprising the Tape- worms, etc. 

 PLAT-Y-RHI'NA (Gr. platus, broad ; rhines, nostrils). A group of the Quadru- 



mana. 



PLE-SI-O-SAU'ETTS (Gr. plesios, near to ; and savxrus, lizard). 

 PLEU'BA (Gr. for the side). The serous membrane covering the lung hi the 



air-breathing Vertebrates. 



PLEU'BON (Gr. pleuron, a rib). The lateral extensions of the shell of Crustacea. 

 PLU'TE-US (Lat. for a pent-house). The larval form of the EcHnoidea. 

 PNEU-MAT'IC (Gr. pneuma, air). Filled with air. 

 PNEU-MAT'O-CYST (Gr. pneuma, air; and Icustis, cyst). The air-sac or float of 



certain of the Oceanic Hydrozoa (Physophoridce). 



PNEU-MAT'O-PHOBE (Gr. pneuma, air ; andphero, I carry). The proximal dilata- 

 tion of the ccenosarc in the Physophoridce which surrounds the pneumatocyst. 

 PNEU-MO-SKEI/E-TON (Gr. pneuma,' and sTceletos, dry). The hard structures 



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

 POD-OPH-THAL'MATA (Gr. pous, foot; and ophthalmos, eye). The division of 



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

 POD-O-SOM'A-TA (Gr. pous, foot : soma, body). An order of Arachnida. 

 PO-EPH'A-GA (Qi.poe, grass ; phago, I eat). A group of the Marsupials. 

 POIS'EBS. 

 POL'LEX (Lat. for the thumb). The innermost of the five normal digits of the 



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

 POL-Y-CYS-TI'NA (Gr. polus, many ; and Tcustis, a cyst). An order of Protozoa, 



with foraminated siliceous shells. 

 PO-LYG'A-MOUS (Gr. polus ; and gamos, marriage). 

 POL-Y-GAS'TEI-CA (Gr. polus ; and gaster, stomach). The name applied by 



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



stomachs. 



POL'Y-PA-BY (Gr. polus; and pario, I produce). The hard chitinous cover- 

 ing secreted by many of the Hydrozoa. 

 POL'YPE (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 



Codenterata,QT: even to the Polyzoa. 

 POI/Y-PIDE. The separate zooid of a Polyzoon. 



POL-YP'I-DOM. The dermal system of a colony of a Eydrozoon, or Polyzo'un. 

 POL'Y-PITE. The separate zooid of a Hydrozoon. 

 POI/Y-STOME (Gr. polus, many ; and stoma, mouth). Having many mouths ; 



applied to the Acinetce among the Protozoa. 

 POL-Y-THAL'A-MOUS (Gr. polus; and thalamos. chamber). Having many 



chambers ; applied to the shells of Foraminifera and Cephalopoda. 

 POL-Y-ZO'A (Gr. polus; and zo'on, animal). A division oi the Molluscoida. 



comprising compound animals, such as the Sea-mat. Sometimes called 



