Pericardium. The chamber containing the heart. 



Periostracum. The epidermal covering of some shells, as Succinea. 



Pervious. Very narrowly open, as the umbilicus in some snails. 



Phytophagus. Vegetable-feeding. 



Pilose. Covered with hairs. 



Pinnate. Branched like a feather, as the gills of some mollusks. 



Plaited. Folded. 



Planorboid. Flat and orb-like, as some snails. 



Pleurae. Eelatiug to the side of a body. 



Plexus. A network of vessels, as the form of the lungs in snails. 



Plicated. Made up of folds. 



Plumose. Resembling plumes. 



Polygonal. Having many angles. 



Polymorphous. With many forms. 



Porcellanous. Like Porcelain. 



Post-basal. Beyond or near the base, as the posterio-ventral part of Lampsilis. 



Prismatic. Like a prism. 



Prodissoconch. The embryonic shell. 



Prosodetic. A term applied to the area in opisthodetic Ligaments, lying in front 



of the umbones and forming the luuule. 

 Protoconch. The embryonic shell. 

 Protract. To push out. 



Protractor pedis. The foot protractor muscle. 

 Protrusile. Capable of being pushed out. 

 Proximal. The nearest end of an object. 

 Pseudocardiuals. False cardinal teeth. 

 Pseudolaterals. False lateral teeth. 

 Pulsation. A throb, as the throbbing of the heart. 



Pupiform. Like a pupa ; one of the stages in the development of an insect. 

 Pustulate. Covered with pustules, or little pimples. 

 Pustulose. Same as above. 

 Pyramidal. Having the form of a pyramid. 

 Pyriform. Shaped like a pear. 



Quadrangular. Having four corners, as some Unios. 

 Radiated. Extending from a common center, as the rays on some Unios. 

 Reflected. Bent backward, as the lip in some snails, or the cusps in the lingual 



membrane. 



Reflexed. Same as above. 

 Renal. Relating to the kidneys. 

 Reticulated. Resembling a network, as when the longitudinal and spiral lines 



cross in a snail. 



Retractile. Capable of being drawn in, as the eye peduncles in laud snails. 

 Retractor pedis. Foot retractor muscle. 

 Reversed. Turned the contrary way. 



ICO 



