Two Boyson bicycles died yesterday after being struck by a car in Datonsville, Md.,, bringing to seven the number of area highway fatalities at the end of the first full day of the Memorial Day weekend.

As of last night, three persons had been killed in Maryland and four in Virginia since the official 6 p.m. Friday opening of the holiday period.

Baltimore County police said Daniel S. Kim, 8, and Geoffrey M. Garrison, 7, both of Catonsville, were riding their bicycles southbound on Montrose Avenue about 6 p.m. Friday when they were hit by a car that also was traveling southbound. No charges have been filed.

Both boys were thrown about 90 feet and suffered severe head injuries. They were flown to Johns Hopkins University Hospital. Both died yesterday afternoon.

A 20-year-old Navy enlisted woman was killed on I-64 in Hampton, Va., yesterday when the motorcycle on which she was a passenger was sideswiped by a van, throwing her into traffic. Police said the van, described as blue, failed to stop.

Trooper Roy Richards said the accident occurred when the motorcycle was hit and forced from the westbound roadway across the median strip and into eastbound traffic. The woman's helmet became lodged against the axle of a car that passed over her, Richards said, and she was dragged 80 feet before the car's driver was able to stop. She was pronounced dead at the scene.

Her name was being withheld pending notification of relatives. Richards said the driver of the motorcycle landed on the median strip and received only minor injuries.

Police were searching for the van last night and asked that anyone who witnessed the accident call the state police division in Chesapeake.

In Montgomery County, 21-year-old Walter Evans was killed when the jeep he was driving overturned as he turned onto Great Seneca Highway from Middlebrook Road shortly before 2 a.m. yesterday, police said.

Police said Evans appeared to have been speeding when he turned on the wet road. The jeep skidded and flipped over. Two passengers were uninjured, police said. Evans was pronounced dead at Shady Grove Hospital at 2:30 a.m.

Elsewhere in Virginia, three others died this holiday weekend, state police reported.

Ronald Coleman Jones, 24, of Dryden, died in a single-car accident on U.S. 58 in Lee County at 8:35 p.m. Friday. He was the driver of the car, state police said.

Paul Lester Sapp, 47, of Salem, a pedestrian, was struck by three cars on a busy Roanoke city street at 9:12 p.m. Friday. He died later at Roanoke Memorial Hospital.

Carl Austin Fairbanks, 20, of York County, was pronounced dead at the scene of a two-car collision on Virginia 105 just west of U.S. 17, at 3:10 a.m. yesterday.