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| a calculus or concretion found in the stomach or intestines of certain animals, esp. ruminants, formerly reputed to be an effective remedy for poison. |
| a screen or mat covered with a dark material for shielding a camera lens from excess light or glare. |
oystershell scale
a species of insect in the armoured scale family, Diaspididae (order Homoptera), that is found on woody plants and secretes a hard, tough protective covering that resembles a miniature oystershell. Despite its small size, the oystershell scale can inflict great damage on the trees and shrubs on which it lives. Control is by dormant, or horticultural, oil spray and natural enemies such as birds, mites, and parasitic wasps.
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