TERMS UNIVALVES. ll 



" Ears are two processes on each side of the 

 beak ; the Pecten, or scallop, is an example. 

 (Plate 3, i.) 



" Sinus, in bivalve shells, is a small hollow 

 in the hinge. 



" Byssus, or beard, is an appendage com- 

 posed of silky threads, by which the muscle and 

 Pinnafasten themselves to the rocks. (Plate 3,/.) 



" Cordiform is a term applied to heart-shaped 

 shells. 



^' A cartilage is the same as a ligament. When 

 the valves of a shell are very nearly flat, they are 

 said to be compressed : when a valve has teeth, 

 it is said to be dentated. 



" When the valves of a shell do not shut close, 

 they are said to be gaping. (Plate 4, My a.) 



" A muscle is a fleshy, pliant organ, by which 

 the animal is attached to its shell. J have already 

 pointed out to you the impressions of those 

 muscles within bivalve shells. 



" A suture is a toothed joint, in bivalves. 



" A shell with ears is said to be auricled. 



" The third division, Univalve shells, have 

 also their several parts. The first section has a 

 regular spire. Here are two shells of this section. 

 Valuta and Buccinum, both sawed asunder, in 

 order to show the interior structure of the shell. 

 (Plate 3.) The aperture, or opening, being 



