BOSTON — Amtrak says it will now allow passengers on some Northeast routes to bring along their pets.Under the program announced Thursday, passengers can take a cat or small dog on trips up to seven hours long.The service is available on the Boston to Lynchburg, Newport News, and Norfolk, Virginia, on the Northeast Regional service lines, as well from Boston to Brunswick, Maine, on the Downeaster route.Pet owners will have to pay an extra $25 to make a reservation.