What is Capita?

Legal Definition
Heads, and, figuratively, entire -bodies, whether of persons or animals. Spelman. Persons individually considered, without relation to others, (polls;) as distinguished from stirpes or stocks of descent. The term in this sense, making part of the common phrases, in capita, per capita, is derived from the civil law. Inst. 3, 1, 6. See Capita, per.
-- Black's Law Dictionary
Legal Definition
-- Ballentine's Law Dictionary