Revolving lines. Spiral lines on a snail shell which run parallel with the sutures. 

 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. In the form of a rostrum. 

 Rudimentary. Not fully formed; imperfect. 

 Kugose. Rough or wrinkled, as parts of some shells. 

 Sacculated. Somewhat like a sac, or composed of sac-like parts. 

 Scalar or scalariform. Resembling a ladder. 

 Schizodont. With few teeth, consisting of one or two cardinals or laterals, 



as in Unio. 



Scutellum. The projecting or pinched parts in front of the umboues in Pisidiurn. 

 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 laud snails. 

 Semielliptic. Half elliptical. 

 Semiglobose. Half, or not quite globose. 

 Semilunate. Half lunate. 

 Semioval. Half, or not quite oval. 

 Serrated. Notched, like the teeth on a saw. 

 Serriform. In the form of series. 



Sessile. Attached without a stem, as the eyes in some water snails. 

 Shouldered. Ridged, as the whorls in some snails. 

 Sigmoid. Shaped like the letter S. 

 Siliceous. Made up of silex. 

 Siuistral. Having the aperture on the left side. 

 Sinuous. Curved in and out, as the edge of some bivalves and the lips of some 



snails. 

 Spatulate. In the form of a spatula, a nat-bladed instrument used by druggists 



in pulverizing drugs. 

 Spherical. Shaped like a sphere. 



Spiral. Wound about a central cavity, as the whorls of snails. 

 Striated. Marked by lines or stria?. 

 Subangulated. Moderately angled. 

 Subcarinated. Moderately carinated. 

 Subcentral. Not quite in the center 

 Subcircular. Not quite circular. 

 Subconical. Moderately conical. 

 Subcylindrical. Moderately cylindrical. 

 Subequal. Not quite equal. 



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