206 GLOSSARY. 
Sessile, low, dwarf. 
Sinuous, waved. 
Sinus, a deep cut, as in the lip of the Murex Babylonius. 
Slope, the side from the beaks. 
Spinous, having prickles or thorns. 
Spire, is formed by the whole of the upper whorls. 
Stria, lines, flat or slightly raised: they are called longitudinal, 
when they run from hinge to margin: transverse, when in 
a contrary direction: and concentric, when they form seg- 
ments of circles. 
Subcordate, approaching the form of a heart. 
Subpellucid, not quite clear. 
Subulate, tapering. 
Superior, see Margin. 
Suture, a toothed joint. 
Syphon, a prolonged tube running through the partitions of 
chambered shells. 
Teeth, (in Univalves), angular plaits, as on the pillar lip of Vo- 
lutes: (in Bivalves), pointed protuberances within the hinge, 
by which the valves are united. They are called: alter- 
nate, when the teeth of one valve are received between the 
teeth of the other valve: articulated, when the tooth is re- 
ceived into a corresponding cavity in the opposite valve: 
cardinal, the central tooth or teeth of the hinge: compress- 
ed, when flattened: erect, perpendicular to the plane of 
the hinge: forked, having the point divided into two: Jon- 
gitudinal, when it extends along the margin. 
Tubercle, a protuberance or knob. 
Tuberculated, having elevations resembling warts. 
Tubular, (applied to Multivalves), when the greater part of 
the shell is cylindrical. 
Turbinated, when the belly of the shell is large in proportion 
to the spire, which seems to proceed from the centre, 
