Each country in the European Union has its own definition of a forest and the European Commission has defined forestland as having at least 20% canopy closure (10% in the Mediterranean forests) and a minimum area of 0.5 ha. (1 ha. = 0.01 kmÂ²). Elsewhere, the definition of a tree can vary.
Lunula: the crescent-shaped area at the base of the human fingernail.
The radula (plural radulae or radulas) is an anatomical structure that is used by molluscs for feeding, sometimes compared rather inaccurately to a tongue.It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters the esophagus.The radula is unique to the molluscs, and is found in every class of mollusc except the bivalves.Within the gastropods, the radula is used in feeding by both herbivorous and carnivorous snails and slugs.n most of the more ancient lineages of gastropods, the radula is used to graze, by scraping diatoms and other microscopic algae off rock surfaces and other substrates. Predatory marine snails such as the Naticidae use the radula plus an acidic secretion to bore through the shell of other molluscs.