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 (pi. 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 (pi. xxviii, fig. 25). 



Parivincular. A ligament "which may be compared to a cylinder split 

 on one side, attached by the several edges, one edge to each valve." (Dall.) 



Patelliform. Shaped like a flattened-out cone, as an Ancylus (pi. xxx, 

 fig. 29). 



Patulous. Open and spreading, as the aperture in some univalves (pi. 

 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 or clear, 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 (pi. xxxii, fig. 7). 



Pleurae. Relating to the side of a body. 



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



Plicated. Made up of folds (pi. 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. 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 lunule. 



Protoconch. The embryonic shell. 



Protract. To push out. 



Protractor pedis. The foot protractor muscle. 



Protrusile. Capable of being pushed out. 



