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THE NATURAL HISTORY SURVEY. 387 
Oviparous. Bringing forth young in an egg which is hatched after it 
is laid. 
Ovisac. A pouch in which the eggs or embryos are contained. 
Ovoviviparous. In this case the young are formed in an egg but are 
hatched inside the parent. 
Papillose. Covered with many little bulgings or pimples (pl. xxiv, 
fig. 2). 
Parallel. Having the same relative distance in all parts, as when the 
spiral lines in univalve shells are the same distance apart all the way 
around (pl. xxviii, fig. 25). 
Parivincular. A ligament “which may be compared to acylinder split 
on one side, attached by the several edges, one edge toeach valve.’ (Dall.) 
Patelliform. Shaped like a flattened-out cone, as an Ancylus (pl. xxx, 
fig. 29). 
Patulous. Open and spreading, as the aperture in some univalves (pl. 
XxxIv, fig. 1). 
Paucispiral. Only slightly spiral, as some opercula. 
Pearly. Having a substance like pearl, as the interior of Unio. 
Pectinate. Like the teeth of a comb, as the gills of some mollusks. 
Pedal. Pertaining to the foot. 
Pedunculated. Supported on a stem or stalk, as the eyes of land 
snails. 
Pellucid. Transparent orclear, as the shells of some snails; e. g. Vit- 
rea, 
Penultimate. The whorl! before the last in univalve shells. 
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 (pl. xxxii, fig. 7). 
Pleurz. Relating to the side of a body. 
Plexus. A network of vessels, as the form of the lungsiin snails. 
Plicated. Made up of folds (pl. xxii, fig. 2). 
Plumose. Resembling plumes. 
Polygonal. Having many angles. 
Porcellanous, Like porcelain. 
Post-basal. Beyond or near the base, as the posterio-ventral part of 
Lampsilis. 
Prismatic. Likea prism. 
Prodissoconch. The embryonic shell. 
Prosodetic. A term applied to the area in opisthodetic ligaments, 
lying in front of the umbones and forming the lunule. 
Protoconch. The embryonic shell. 
Protract. To push out. 
Protractor pedis. The foot protractor muscle. 
Protrusile. Capable of being pushed out. 
