存储错误，帮我看看吧

create proc InquiryTO(@StartStop varchar(32),@EndStop varchar(32))
as
begin
     select
          sr1.Stop as 起始站点，
          sr2.Stop as 目的站点，
          sr1.Route as 乘坐线路，
          sr2.Position-sr1.Position as 经过的站点数
     from
         stop_route sr1,
         stop_route sr2
     where
         sr1.Route=sr2.Route
         and sr1.Position<sr2.Position
         and sr1.Stop=@StarStop
         and sr2.Stop=@EndStop
end  
错误提示：消息 137，级别 15，状态 2，过程 InquiryTO，第 18 行
必须声明标量变量 "@StarStop"。