Rose Kennedy, the 91-year-old matriarch of one of America's most prominent political families, was admitted to St. Mary's Hospital in West Palm Beach, Fla., last night for "observation," a hospital spokesman said.

Spokeswoman Ruth Hardy said that Kennedy was "resting comfortably" in a private area of the hospital and was in "stable condition."

Rose Kennedy was brought to the hospital from her Palm Beach home by family members about 8 p.m. "Apparently, she just wasn't feeling well," said Hardy.

Kennedy was hospitalized last November after complaining of chest pains during mass at St. Edward's Roman Catholic Church in Palm Beach.

Last weekend, she was unable to attend ceremonies in Boston in memory of President John F. Kennedy, one of her sons, who would have turned 65 on Saturday. About 4,000 people gathered by a mist-shrouded Boston Harbor for swimming and foot races to mark the birth date of the 35th president, who was assassinated in 1963.

Sen. Edward M. Kennedy, 50, the youngest of the Kennedy brothers, planted a rosebush shipped in from the family residence in Hyannisport outside the John F. Kennedy Presidential Library. He also sliced into a 1,500-pound, 8-by-12-foot birthday cake made for the occasion.

"It was always a happy day," said Kennedy of his late brother's birthday. "It is appropriate that this be a happy occasion."

Other family members at the event included Kathleen K. Townsend, eldest daughter of the late Robert F. Kennedy, and her daughters, Meaghan and Maeve.

Neither former first lady Jacqueline Kennedy Onassis nor the late president's two children, John and Caroline, attended, according to a library spokesman.

Paul McCartney went home to Penny Lane in Liverpool, England, last weekend as best man in the marriage of younger brother Michael McCartney and 21-year-old dress designer Rowena Horne. Outside St. Barnabas Church 500 people gathered to catch a glimpse of the former Beatle's arrival, but McCartney and wife, Linda, slipped in through a side door.

It was the second marriage for the younger McCartney, 38; his three daughters from his previous marriage were bridesmaids. During the ceremony the Rev. Bill Harrington reminded guests that Paul McCartney used to sing at the church for 10 shillings--about $1--in his pre-Beatle years.

Actress Ellen Burstyn has been elected the first woman president of Actors' Equity Association, succeeding Theodore Bikel, who has headed the 30,000-member actors' union for nine years.

Burstyn, who starred in such movies as "The Exorcist" and "Resurrection" and won an Academy Award as best actress for "Alice Doesn't Live Here Anymore," defeated actress Lynn Oliver by a mail referendum vote of 6,112 to 2,131.

The theft of four 17th-century Dutch and Flemish paintings--including a reputed Rembrandt--from the Detroit Institute of Arts was probably "an inside job," a museum official said yesterday.

Authorities are offering a reward, possibly as high as $30,000, for information leading to the recovery of the paintings, valued at more than $300,000.

Museum spokesman Bob Rodgers said the institute's insurance company must first approve the offer but such rewards normally are about 10 percent of appraised value.

"It would appear that it was an inside job," museum security chief Adolph L. Smith said, because if an outsider had sneaked in, alarms would have gone off. And, he said, if a stranger had been near the basement storage area where the paintings were being temporarily stored, museum workers would have asked to see museum identification.

Last week's auction of Bing Crosby's personal belongings, including film posters, records and old cars, fetched at least $300,000, a spokeswoman for the auction said. But, she added, a number of items were withdrawn and would probably be auctioned later.

Asked what she intended to do with the money, Kathryn Crosby, the singer's second wife, said, "I will think of something.

"I just needed more room in our mansion here."

During the four-day auction Crosby sat at the back of the hall, nodding her approval of the bidding. She also brought in food and drink for the crowd of 500 on Saturday.