388 THE CHICAGO ACADEMY OF SCIENCES. 
Proximal. The nearest end of an object. 
Pseudocardinals. False cardinal teeth. 
Pseudolaterals. False lateral teeth. 
Pulsation. A throb, as the throbbiug of the heart. 
Pupiform. Like a pupa; one of the stages in the development of an 
insect. 
Pustulate. Covered with pustules or little pimples (pl. xxiv, figs. 1, 2). 
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 (pl. xxviii, fig. 26), 
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 land 
snails. ; 
Retractor pedis. Foot retractor muscle. 
Revolving lines. Spiral lines on a snail shell which run parallel with 
the sutures (pl. xxxv, fig. 5). 
Rhombic. Having four sides, the angles being oblique. 
Rhomboid. Four-sided, but two of the sides being longer than the 
others. 
Rimate. Provided with a very small hole or crack, as some snails in 
which the umbilicus is very narrowly open. 
Roundly lunate. Rounder than lunate (which see). 
Rostriform. Inthe form of a rostrum. 
Rudimentary. Not fully formed; imperfect. 
Rugose. Rough or wrinkled, as parts of some shells (pl. ix, fig. 1). 
Sacculated. Somewhat like a sac, or composed of sac-like parts. 
Scalar. Resembing a ladder. 
Schizodont. With few teeth, consisting of one or two cardinals or lat- 
erals, as in Unio. 
Scutellum. The projecting or pinched parts in front of the umbones 
in Pisidium. ! 
Scutum. The pinched parts behind the ligament in Pisidium. 
Secreted. Produced or deposited from the blood or glands, as the 
shell material in mollusks. 
Semicircular. Half round or circular, as the aperture in some snails. 
Semidentate. Half toothed, as the parietal wall in some land snails. 
Semielliptic. Half elliptical. 
Semiglobose. Half, or not quite globose. 
Semilunate. Half lunate. 
Semioval. Half, or not quite oval. 
