678 GLOSSARY. 



Pectinated. (Lat. pecten, a comb.) Toothed like a comb. 



Pkctinibranchiata. (Lat. pecte/i, a comb; ira^^cAia, gills.) The order of Gas- 

 tropods in which the gills are shaped like a comb. 



Pediform. (Lat. pes, a foot. ) Shaped like a foot. 



Peduncle. From the Latin pedunculus, a stalk. 



Pedunculated. Suspended or supported by a stalk. 



Pelagic (Gr. pelagos, sea.) Belonging to the deep sea. 



Pentacrinite. (Gr. penta, five ; krinos, hair.) A pedunculated star-fish with five 

 rays : they are, for the most part, fossil. 



Pergameneous. (Lat. pergamen, parchment.) Of the texture of parchment. 



Periostracum. (Gr. peri, around ; ostrakon, shell.) The membrane analogous to 

 scai'f-skin, which covers shell. 



Peristaltic. (Gr. peri; stello, to range.) The vermicular contractions and motions 

 of muscular canals, as the alimentary, the circulating, and generative tubes. 



Peritoneal. (Gr. peritonaios, the covering of the abdomen.) Restricted to the 

 lining membrane of that cavity. 



Peritrema. (Gr. peri, around; trema, hole.) The raised margin which sur- 

 rounds the breathing holes of scorpions. 



Petiolate. (Lat. petiolus, a fruit stalk.) Ducts supported or suspended by a 

 slender stalk. 



Pharynx. The dilated beginning of the gullet. 



Pharyngeal. Belonging to the pharynx. 



Phragmocone. (Gr. phragma, a partition ; konos, a cone.) The chambered cone 

 of the shell of the Belemnite. 



Physograde. (Gr. physis, air ; and gradior, I proceed.) The Acalephes that 

 swim by means of air-bladders. 



Phytophagous. (Gr. phuton, a plant ; phago, I eat.) Plant-eating animals. 



Pigmental. (Lat. pigmentum, paint.) The cells which secrete the coloured par- 

 ticles of the skin and eye, and the membrane formed by such cells. 



Pinnate. (Lat. pinna, a feather or fin.) Shaped like a feather, or provided with fins. 



Planula. (Lat. planus, flat.) A name applied to the flat ciliated form of larva, 

 under which many polypes first quit the egg. 



Plasma. ( Gr. plasma, mouldablc matter.) The fluid part of the blood, in which 

 the red corpuscles float : also called liquor sanguinis 



Plastron. The under part of the shell of the crab and tortoise. 



Plexus. (Gr. pleko, I twine.) A bundle of nerves or vessels interwoven or 

 twined together. 



Pleiocene. (Gr. pleion, more ; kainos, recent.) The tertiary strata, which are 

 more recent than the miocenc, and in which the major part of the fossil testacea 

 belong to recent species. 



Pleistocene. (Gr. pleistos, most ; kainos, recent.) The newest of the tertiary 

 strata, which contains the largest proportion of living species of shells. 



Plicae. (Lat. plica, a fold.) Folds of membrane. 



Plumos. (Lat. pluma, a feather. ) Feathery, or like a plume of feathers. 



Pneumatic. (Gr. pneuma, breath.) Belonging to the air and air-breathing organs. 



PoDOPHTHALMA. (Gr. pous, a foot ; ophthalmos, an eye.) The tribe of Crustacea 

 in which the eyes are supported upon stalks. 



PoLYGASTRiA. (Gr. polus, many ; gaster, a stomach.) The class of infusorial ani- 

 malcules which have many assimilative sacs or stomachs. 



Polypi. (Gr. polv^ ; pous, a foot.) The class of zoophytes with many prehensile 

 organs radiating from around the mouth. 



Prolegs. The wart-like tubercles which represent legs on the hinder segment of 

 caterpillars. 



Prothorax. (Gr. pro, before, and thorax.) The first of the three segments which 

 constitute the thorax in insects. 



Psychical. (Gr. psuche, the soul.) Relating to the phenomena of the soul, and 

 to analogous phenomena in the lower animals. 



Pteropoda. (Gr. pteron, a wing ; pous, a foot.) The class of MoUusca in which 

 the organs of motion ai'c shaped like wings. 



Pulmograde. (Lat. pulmo, a lung ; gradior, I walk.) The tribe of Medusa; 

 which swim by contractions of the respiratory disc. 



Pulmonata. (Lat. pulmo.) The order of Gastropods that breathe by lungs. 



