222 EXPLANATION OF TERMS. 



Fluviatile. Belonging to fresh water; from 



fluviws, a river. 

 Globose, Globular. Approaching the form of a 



globe. 

 Genus. A separate family, distinguished from 



all others by certain permanent marks, 



called generic characters ; from gen us, a 



kind. 

 Gibbous. Convex, swelling out, from gibbus, 



a swelling, a hunch on the back. 

 Gaping. The valves so partially closing, that 



the margins do not touch at every part of 



the circumference. 

 Imbricated. Lying one over another like the 



tiles of a house ; from imbrex, a tile. 

 Iridescent. Displaying the varied colours of 



the rainbow ; from iridescere, to shine 



like a rainbow, in Latin iris. 

 Insterstice. Space between one part and another. 

 Inequivalve. Having unequal valves ; from in, 



not, equ us, equal, and valve. 

 Inequilateral. Having sides not uniform ; 



from in, not, equ us, equal, and latera, 



sides. 

 Involuted. Rolled inwards ; from involut us, 



rolled up in. 

 Littoral. Belonging to the shore ; from litt us, 



a shore. 



Lateral. At the sides ; from later a, sides. 

 Longitudinal. In the direction of the length of 



a shell; ( i. e. ) from the apex to the 



base. 



