VIRTUALLY BURIED for 40 years, the Spanish cinema -- and indeed the Civil War itself -- at last has returned to the light.

A remarkable series of 16 films, made since censorship by church and state ended, will be shown here at the American Film Institute theater tonight through Feb. 14. They cover subjects that were taboo under the Franco regime, from terrorism to sex change.

Most of all, they cover the Civil War. Perhaps the centerpiece of the whole series is "The Old Memory," a three-hour documentary with newsreels and interviews that towers above the French "The Sorrow and the Pity," to which it is usually compared.

For one thing, an amazing number of major figures from the war, some still in exile, tell their stories, including the rightist leader Gil Robles and the celebrated La Pasionaria, whitehaired today but fiery as ever. She and Robles are matched in a sort of debate by remote control, each responding to the other's claims. Anarchists, Comunists, generals, Falangists, all the factions are represented here.

We watch the progress of the tragedy, from the wild triumph of the republic on April 14, 1931, to the moment-moment descripotion of how the fighting started; from the siege of Madrid (with pictures of the historic warfare), to the final, bitter war-within-a-war between communists and anarchists that helped defeat the loyalist cause, as the participants reveal.

Even more powerful than the shots of people fighting and being killed are a couple of interviews, one with a man who was called to witness the execution of a friend, the other with a man who served on a firing squad.

In this one film -- with its faded scenes of cheering crowds, children digging trenches, homemade tanks, executions and people falling dead in the streets during an air raid -- all the forbibben fury against Franco comes alive, after a generation of being expresed in films only through allegory and indirection.

"The Old Memory" will be screened Jan. 14, at 8:30 p.m.

A companion piece, "The Long Vacation of 1936" (Jan. 21 at 6:30 p.m., Jan. 22 at 8:30p.m.), shows the effect of the war on some fictional bourgeols families who hole up at their summer resort for the duration.

This picture has all the characteristics of the new Spanish film, or at last the examples in hand. It is excruciatingly slow to start, just as the war itself began, in a curious air of unreality. Men with guns drive past in trucks. Shouts fill the night. From the radio come those rasping, important-sounding voices that were to be part of life for nine more years.

The pace is deliberate, dignified, serious. The story belongs to the children, who first love their endless vacation but gradually feel the war's effects.

Children, in fact, seem much more a part of movies in Spain than in other countries. If they are not actually the central figures, as in "The Spirit of the Beehive" (Jan. 27 at 6:15 p.m., Jan. 28 at 8:30 p.m.) or "Black Brood" (Jan. 10 at 6:30 p.m.), they show up continually, whether as plot devices, symbols or just minor characters.

Spanish films are fairly homogeneous in mood and tone and narrative techniques. For instance, there is a fascination with old snapshots. These are used most movingly in "My Dearest Senorita" (Jan. 23 and 24 at 6:30 p.m.).

During the credits we see old snaps of family groups, which are nice but tell us little. Halfway through the picture the central character, a 44-year-old spinster, learns that she is physically not a woman. Now we see the photos again, and we zoom up to the face of a young girl in frills, a face haunted with dread and secret knowledge.

The picture has been called a black comedy (that handy pigeonhole for the films you don't quite get), and certainly it is funny. But it is far more than that. It is a valentine to a love that never asks why.

The Spanish penchant for surprise endings never worked better than in this picture.

Carlos Saura, the veteran director who will be at the premiere here tonight, along with other Spanish film figures uses the snap ending with devastating effect, especially in his taut "Blindfolded" (Jan. 30, 8:30 p.m.), with Geraldine Chaplin, a protest against torture.

Though torture is never seen, it is eerily evoked by scenes in a denstist's office (the drill, the blinding light, the bloody saliva) and in, again, old snapshots of kids playing war, and simply in long shots of a man listening in an underground garage. Just standing there, listenting. It works. And despite the sometimes cryptic editing, which jumps about in time rather more than it needs to, the movie itself works so well that we absolutely need that explosion of violence at the very end.

Another Saura work is the leadoff picture, "Mon's 100 Years Old," showing tonight at 7:30 in the Eisenhower Theater, the sequel to his 1972 movie which attacked Spain's corrupt establishment via a family of grotesques. The new film is much more lighthearted, a bizarre mixture of Fellini and that old French peasant comedy, "Goupi Mains Rouges."

Geraldine Chaplin stars in this, as she does in the touchng "Elisa My Love" (Jan. 11 at 6:30 p.m., Jan. 13 at 5:30 p.m.) with Fernando Rey.

Saura, who worked under the Franco regime in the 1950s, first came to the attention of American audiences in 1967 with "The Hunt," a landmark in cinema gore. The scences in which the hunters shoot each other in the face at close range are bad enough, but the shot that really sticks is a cutaway view of a rabbit run where a ferret meets a rabbit and calmly bites it right between the eyes and hangs on. These aren't actors.

One could argue that, under censorship, the mordant is replaced by the merely morbid. a case in point is the comparison of Saura with the great Luis Bunuel, who spent the Franco years in exile and whose films are probably the last word in mordancy for our time or any other.

Also in the series are "Poachers" (jan. 7, at 8:15 p.m., Jan. 8 at 8 p.m. another symbolic portrait of violence; Anguish" (Jan. 15 at 6:30 p.m.), a lush retelling of an 1890s novel of greed and desire featuring a priest who has fallen in love with a girl, certainly a taboo before this; "The New Spaniards" (Jan. 17 at 6:30 p.m.), a satire on American business methods applied to Spain.

The second phase of the series includs "The Sabina," Feb. 1; "Blindfolded," Feb. 3; "To an Unknown God," Feb. 4; "The Brunt City," Feb. 6; "What Max Said," Feb. 11, and "Sleep Walkers" Feb. 14.