Scabious, rough, rugged. Scalloped, indented at the edges. Scutellated, shield-shaped. Seam, line formed by the union of the valves. Semi, the half. Semi-cordate, half heart-shaped. Semi-orbicular, shape of a half globe. Semi-lunar, shape of a half moon. Septiform, shape of a partition. Serrated, like the teeth of a saw. Sessile, sitting or seated. Seta, a bristle. Setaceous, covered with bristles. Setiferous, bearing bristles. Sinister valve, is the left valve. Sinus, a groove or cavity. Siphunculus, a cylindrical perforation as in the Nautilus, Spirula, &c. Spatulate, rounded and broad at the top. Species, the division of a family or genus. Spiny, thorny. Spinous, like a hedgehog. Spire, all the whorls in univalves except the one in which the aperture is situated, which is termed the body. Spiral, twisted like a corkscrew. Squamose, scaly. Striated, covered with thread-like lines. Sub, almost. Subarcuated, somewhat arched. Subconic, somewhat conical. Subulate, awl-shaped. Sulcated, furrowed. Summit, the tip or apex. Suture, a hollow line of division in univalves, the spiral line of which separates the wreaths. T. Teeth, pointed protuberances within the hinge in bivalves by which the valves are united. Tentacula, the feelers of snails, which inhabit shells. Tessellated, chequered like a chess board. Testacea, that order of animals covered with a testaceous shell. Testaceous, consisting of carbonate of lime and animal matter. Tortuosity, flexure. Tortuous, twisted. Transverse, crossways. Trapeziform, shaped like a trapezium. Trigonal, having three angles. Truncated, cut short, ending abruptly. Tubercle, knot or pimple. Tuberculated, knotted, pimpled. Tubular, in the shape of a hollow tube. Tunicated, coated. Turbinated, shape like a top or pear. Turgid, swollen. U and V. Valves, the various pieces which compose the shell. Varices, longitudinal ribs in univalve shells. Variety, difference in species. Vaulted, roofed. Ventral, belonging to the belly. Ventricose, inflated, swelled in the middle. Vermiform, worm-shaped. Vertex, the top of a most prominent part. Verrucose, warted. Verticulated, whorled. Umbilicated, having a depression in the centre. Umbo, the round part which turns over the hinge. Undulated, waved. Ungulata, shaped like a horse’s hoof. Unilocular, chambered singly. Univalve, shells of one valve only. Volutions, the turnings of univalves. W. Whorl, a spiral convolution. Z. Zigzag, having reverse turnings and windings. Zoned, surrounded by belts or girdles. INDEX A. Acasta, 32 Acera, 95 Achatina, 102 _Alata_, 135