Semi-cordate, half heart-shaped. Semi-cylindrical, half cylindrical, cut through lengthways. Semi-orbicular, the shape of a half globe. Semi-lunar, the shape of a half moon. Semi-pellucid, somewhat pellucid or shining. Septiform, in the shape of a partition. Serrated, like the teeth of a saw. Serrulated, very minutely serrated. Sessile, sitting or seated. Seta, a bristle. Setaceous, bristly, covered with bristles. Setiferous, bearing bristles. Setose, covered with bristles. Sinister valve, is the left valve. Sinus, a groove or cavity. Siphunculus, a cylindrical canal perforating the partitions in polythalmous shells; for instance, as in the _Nautilus Spirula_. Solitary, generally applied to a single tooth in bivalves. Spatulate, rounded and broad at the top, and becoming narrow like a spatula or battledore. Species, the division of a family or genus, containing such as agree with it in general characters, or such as are derived from one common parentage. Spiny, thorny, covered with thornlike processes. Spinous, having spines like a hedgehog. Spire, all the whorls of univalve shells, excepting the one in which the aperture is situated, which is termed the _body_. Spiral, twisted like a corkscrew. Squamose, scaly. Stellated, starred, consisting of star-like figures. Striated, scored, or covered with fine threadlike lines. Sub, in composition, means almost, or approaching to; as sub-globose, somewhat globular. Subarcuated, somewhat arched. Sub-conic, somewhat conical. Sub-diaphanous, somewhat transparent or clear. Sub-rotund, nearly globular. Subulate, awl-shaped. Sulcated, furrowed. Sulci, furrows or ridges. Summit, the tip or apex. Sature, a hollow line of division in univalve shells, the spiral line of which separates the wreaths. T. Tentacula, the feelers of snails which inhabit shells. Tesselated, checkered like a chessboard. Testacea, the third order of worms, including those which are covered with a testaceous shell. Testaceous, consisting of carbonate of lime and animal matter. Tetragonal, four cornered. Torose, swelling into knobs or protuberances. Tortuosity, wreath, flexure. Tortuous, twisted, wreathed, winding. Transverse, placed across or crossways. When the breadth of a shell is greater than its length, it is called transverse. Trapeziform, shaped like a trapezium. Trigonal, having three angles. Truncated, stunted, cut short or abruptly off at the end. Tubercle, a little knot or pimple. Tuberculated, knotted, pimpled. Tuberosities, prominent knots or excrescences. Tubular, in the shape of a hollow tube. Tubulate, tubulous or hollow. Tunicated, coated. Turbinated, shaped like a top or pear. Turgid, swollen. U & V.