Abstract: A magnetic tape cartridge includes a casing having a tape chamber defined therein for accommodating a reeled magnetic recording tape and, also, box arms protruding outwardly from a front wall section of the casing so as to leave a loading bay that opens upwardly, frontwardly and downwardly and is thus delimited by upwardly, frontwardly and downwardly oriented open areas. The casing includes a lid assembly for selectively concealing and exposing that portion of magnetic recording tape and including front, top and rear lids operatively linked together. The front and top lids are adapted to selectively open and close the frontwardly and upwardly oriented open areas of the loading bay, respectively, while the rear lid is positioned within the loading bay and adapted to selectively open and close a space delimited between the front and the rear lid.