39^ SHELLS AND SHELL-FISH. 



Foliated. Resembling leaves. As used for the external 

 surface of shells, the varices, or spines^ on many of 



I the Murices are foliated, or divided at their margins 

 into leaf-like segments, as in the rosebush Murex ; 

 but applied to the substance, it indicates those bivalves 

 which are composed of thin flat plates, very fragile, 

 and . lying upon each other, as in the common and 

 pearl oysters. Sometimes the spines of bivalves are 

 partly foliated, as in the genus Spondylus, 



Front. The front of a shell is obviously that near 

 to which the head of the animal protrudes : but this 

 term, however objectionable, is given to the under 

 surface of spiral shells, or that where the aperture is 

 placed, in contra-distinction to the back. 



Fusiform, or spindle-shaped ; thickest in the middle, 

 and attenuated or tapering to the extremities. Fusus, 

 Fasciolaria, and many mitres, are more or less of this 

 form. 



Gaping. A bivalve is called gaping, when any part of 

 the margins do not touch. 



Gibbous, or humped. Any part of a shell more par- 

 ticularly elevated above the surface, or unusually so in 

 comparison to other species, is termed gibbous, as 

 Strombus gibbosus. 



Granulated, or grained. Marked by elevated, close set, 

 and regular dots, resembling grains : this appearance 

 is very common at the base of the predaceous spiral 

 genera. 



Hinge margin in bivalves, see Dorsal margin. The 

 hinge is composed of the ligament, the cartilage, and 

 the teeth. 



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

 stance. 



Imbricated. Plates or folds laid over each other, like 

 tiles on the roof of a house. 



