These are dark brown because of the dense concentration of symbiotic algae known as zooxanthellae that they contain.

Its concave lower surface houses a dense concentration of larger nectar glands, which are otherwise absent from the lid.

Four conditions were necessary to enable the diversity essential for urban renewal: mixed uses, small walkable blocks, mingling of building ages and types, and a sufficiently dense concentration of people.

Many in the industry allege that this dense concentration of talent, entrepreneurship and supply stores functions like an ecosystem in which each of the parts help sustain the whole.

It may be found in dense concentrations or singly.