WHEN MOST of us think of Spanish dancing, we think of flamenco, that dashingly rhythmic combination of rat-a-tat heels, aristocratic postures and swirling skirts. While the flamenco, when performed by a master, is indeed glorious, it represents only one of an immense range of Spanish movement forms: jota, seguidilla, fandango, bolero, to name but a few.

That's not all. Consider the regional variations on each of these dances. Then think about all those foreign inhabitants of Spain through the ages, and the mark they left on that country's culture. No wonder a Spanish dance zealot like Marina Keet never runs out of material to highlight on her annual programs.

Keet, a founding member of the Spanish Dance Society, an international body organized to preserve the teaching and performance of the art form -- created quite a stir when she set up shop in Washington four years ago. Though she herself is not of Spanish origin, and no longer dances professionally, she has proved to be a quadruple threat as producer/director/instructor/choreographer. She has trained a fine ensemble, attracts guest dancers and musicians of the highest caliber, and strives always for authenticity.

Each of the two concerts she will present this weekend at Baird Auditorium focuses on specific aspects of Spanish dance. Saturday's performance deals with the seguidilla and the fandango, and features a castanet lecture/demonstration by Jose de Udaeta; Sunday's program highlights regional dances and the jota, and ends with Keet's original ballet "Fiesta Manchega."

MARINA KEET & THE SPANISH DANCE SOCIETY USA -- Saturday at 8 p.m., Sunday at 4:30. Baird Auditorium, Natural History Building, 10th and Constitution Avenue NW. Tickets $10, students $5. Call 357-3030.