The Festival of Moonlit Mews

At the annual Festival of Moonlit Mews, a gathering of femlalas and catboys mingle under lantern‐lit boughs.

Every creature has exactly one head.
Only the catboys have tails (one each); femlalas have none.

By counting carefully, the festival steward reports:

There are 30 heads in total.
Between them they have 12 tails.

How many femlalas were at the festival, and how many catboys?