78 GLOSSARY. 



Pyriform. Shaped like a pear, that is large and rounding 



at one end and gradually tapering a,t the other. 

 Radiating. A term applied to the ribs, striae, bands of 



colour, &c.j when they meet in a point at the umbones 



of a bivalve shell. 



Reflected or reflexed. Turned or folded backwards. 

 Reversed or Sinistral. See Dextral. 

 Septa. The internal laminar division between the whorls of 



most univalve shells. 



Simple. Single, entire, uninterrupted, undivided. 

 Sinistral. On the left side, reversed. 

 Spines. Thin pointed spikes. 

 Spiral. Revolving from a centre. 

 Spire. The cone or pyramid of some univalve shells. The 



spire, in descriptions, includes all the whorls above the 



mouth of the shell. 



Striae, striulce. Small channels in shells. 

 Sulcated. Having grooves or furrows. 



Suture. A seam, stitch, or joining together; applied par- 

 ticularly to the line which marks the joining of the 



whorls of the spire. 

 Tentacle. A filiform process round the mouth of various 



mollusks, being either an organ of feeling, prehension, 



or motion. 



Transverse. Crosswise. 

 Turreted. "When the whorls of univalve shells rise regularly 



above each other, so as to have the appearance of little 



turrets. 

 Umbilicus. The hollow in a spiral shell, occasioned by its 



whorls or convolutions not touching each other. 

 Umbones. The points in bivalve shells which constitute the 



nucleus or apex of each valve, and are generally situated 



near the hinge. 



Univalve, consisting of only one shell or valve. 

 Ventral. The margin of a bivalve shell, opposite the hinge. 

 Ventricose. Bounded out. 

 Whorl or Volution. A wreath, convolution, or turn of the 



spire of a univalve shell. 



