The Ringling Bros. and Barnum & Bailey Circus is coming to town next month with its attraction, a unicorn. Unicorns are mythical beasts, white to symbolize purity and chastity, with a single horn rising from the head. They can only be tamed, legend tells us, by a virgin's touch. There apparently was a virgin in Houston last year when, according to a circus spokeswoman, Kim Turpin, the unicorn showed up and joined the show.

This unicorn looks suspiciously like a white goat with a horn, and last year when the beast was in New York City, some members of the Humane Society complained there was mistreatment of the animal to create the single horn. Turpin argues the animal hasn't been mistreated and said the unicorn is only part of "the whole aura of the show (which) is one of fantasy and dreams coming true." She said the animal's favorite food is rose petals. And, she neglected to add, tin cans. Commencement Speaker Koppel ABC's "Nightline" anchor Ted Koppel may have been the third choice for Stanford University's commencement speaker, but it's not bad coming in third when the first two choices were Soviet leader Mikhail Gorbachev and the widely admired comedian Bill Cosby. Alumnus Koppel, who has a master's degree in speech and drama from the university, wrote to Stanford President Donald Kennedy: "The thought of compelling some of my old professors to listen to me in silence and at least the appearance of rapt attention is almost enough" reason to speak. End Notes

Sightings around town: Austine Hearst, the wife of William Randolph Hearst Jr., yesterday toured the "Treasure Houses of Britain" exhibit at the National Gallery of Art. Her father-in-law was once the baron of San Simeon, so the Hearst family knows a thing or two about big houses and art collecting . . . Frank Sinatra at a quiet dinner Tuesday at the Madison Hotel's Montpelier Room with public relations adviser Joe Canzeri and his wife Tricia and Madison owner Marshall Coyne . . . Shirley Temple Black Monday having dinner at the Vista International Hotel with her son Charles Black, who works at the Department of Commerce. The hotel's chef gave her a chocolate "good ship lollipop," filled with chocolate lollipops. The former ambassador and White House chief of protocol will always be 6 years old with sausage curls . . . Singer John Denver having breakfast yesterday at the Hyatt Regency Capitol Hill, wearing dark glasses and actually eating cereal, just like in his television commercial. The waiter doesn't remember if it was raisin bran. It is known, however, that the hotel does not stock Post Raisin Bran . . .

A tragedy for brilliant Academy Award-winning actress Cloris Leachman. Her 30-year-old son Bryan Englund was found dead Tuesday in a Manhattan YMCA room. Police found two bottles of medication for ulcers and speculated an overdose may have caused the death. Leachman, who had been a regular on the "The Mary Tyler Moore Show," received an Oscar in 1971 for best supporting actress in "The Last Picture Show" . . .

Comedian Bill Cosby was to be in town Friday to receive the Congressional Black Associates Paul Robeson Award in recognition of his dedication to the arts. Cosby, who will be doing a show at the University of Utah in Salt Lake City that evening, will send several members of his family to substitute for him at the 6th Annual Black History Awards dinner at the National Press Club. Picking up the award for him will be his mother Anna Cosby from Shelburne, Mass.; his aunt Clara Waugh from Philadelphia; and his wife Camile's parents, Guy and Catherine Hanks of Silver Spring . . .

That was quite an opening yesterday for the new Westin Hotel at 24th and M streets NW. The kitchen wasn't quite prepared for the turnout of about 350 guests for the ribbon-cutting luncheon and ran out of bread. They had to borrow bread from its older neighbor and competitor, the Grand Hotel, across the street. But going to the official opening was more rewarding than a free lunch. The guests each received a certificate for a free weekend in the luxury hotel, including two breakfasts in bed. That's truly going to be a competitive location when still a third hotel opens on that corner this year . . .