Crossword Genius

Heads are those of Cupid and Psyche, inscribed "To Apollo" (6)

Ross

I believe the answer is:

'heads' is the definition.
('heads' in Latin)

I don't understand the remainder of the clue.

(Other definitions for capita that I've seen before include "Per ..., per head", "'Per ..., for each person (6)'".)

I've seen this clue in Independent.