A DICTIONARY OF TERMS. 



lix 



Sinuous. - Waved, folded, or deeply lobed. The margin of a 

 shell is sinuous, when it bends in and out. 



Sinus. - - A deep cut. The Murex Babylonius has a sinus in 

 the lip. 



Siphon. - A prolonged tube, running sometimes through the 

 partitions of chambered shells. 



Spine. - - A lengthened point either straight or curved. The 

 Thorny Woodcock, Murex Tribulus, has very long 

 spines. 



Spire. - - Each single, or separate turning, or circumvolution 

 in a Univalve shell, is called a spire. 



Spiral. - Univalve shells, having one or more spires, are called 

 spiral. 



Stri^;. - - Very fine lines, either flat or raised, which cross the 

 surface of shells in different directions. When th&y 

 proceed from hinge to margin, they are called longi- 

 tudinal strias, and when in a contrary direction, trans- 

 verse striae. Concentric striae are those which form 

 the segments of circles. 



Striated. - Charged with striae. 



Summit. - The highest part of a shell. In Univalves it is 

 the point of the spire. 



Summit. - The upper part of the valves, in Bivalve shells, is 

 called the summit. It is generally curved inwards, 

 towards the hinge, which it surmounts. 



Suture. - A toothed joint. The valves of some of the Acorn 

 shells are connected by sutures. 



T. 



Teeth. - - Angular plaits upon the pillar lip of Volutes, and 



some other shells. 

 Teeth. - - Protuberances, and fangs, on the hinges of Bivalve 



shells. 

 Tentacula. Delicate, fleshy bodies, with which animals of the 

 class Mollusca, are provided ; they are capable of 

 contraction and extension, and are endued with ex- 

 treme sensibility. The horns of the snail are its 

 tentacula. 



