296 POPULAR CONCHOLOGY. 



Epidermis. The membranous covering of some shells. 

 Epiphragma. A covering to the aperture of some spiral 



shells, which (unlike the operculum) is not attached to 



the animal. (See Operculum.) 

 Equilateral. When the two sides of a Bivalve are equal, 



the bosses being nearly or quite in the middle ; as in 



the cockle. 



Equivalve. When the two valves of a Bivalve are equal 



in size ; as in the cockle. 

 Eroded. Gnawed, or rubbed. 



Fibrous. Resembling fibres : applied to the substance 

 of a shell, it indicates those, like the Pinna, whose 

 fracture presents perpendicular fibres. 



Fluviatile. Living in fresh water. 



Foliated. Composed of thin plates, lying on each other, 



as in the shell of the oyster. 

 Fusiform. Shaped like a spindle, swollen in the middle 



and tapering to each end. 



Gaping. In Bivalves, when, the shell being closed, the 



valves do not touch each other in every part. 

 Gelatinous. Like jelly. 



Hinge. The part where the valves of a Bivalve are 

 united, consisting of ligament and teeth. 



Hyaline. Of a glassy, thin, and semi-transparent sub- 

 stance. 



Inequilateral. When the sides of a Bivalve are unequal 



in length. (See Equilateral.) 

 Inequivaloe. When the valves of a Bivalve are unequal 



in size and shape, as the oyster. (See Equivalve.) 

 Inferior Valve, In adherent Bivalves, that by which the 



shell is attached to other substances. 



