Magnetic disk cartridge having an opening for a magnetic head on a side thereof

A magnetic disk cartridge comprising a cassette shell and a magnetic disk, which is incorporated in the cassette shell such that it rotates, wherein the cassette shell is provided with an opening for insertion of a magnetic head, through which the magnetic head for magnetically recording and reproducing signals is to be inserted from the exterior such that the magnetic head is brought into contact with the surfaces of the magnetic disk or is brought to positions close to the surfaces of the magnetic disk, said opening for insertion of the magnetic head being formed in a side surface of the cassette shell, said side surface being parallel to an axis of rotation of the magnetic disk, and

• a shutter member for opening and closing said opening for insertion of the magnetic head by moving along said side surface of the cassette shell in a direction parallel to said side surface, said shutter member being located only in said side surface of the cassette shell,
• wherein a recess is formed in said side surface of the cassette shell, said recess including the region of said opening for insertion of the magnetic head, and said shutter member is located in said recess such that said shutter member slides in said recess, and
• further wherein a guide member having a guide groove and extending in a direction along which said shutter member slides, is located at said side surface of the cassette shell and at a spacing from the surface of said recess, and a portion of said shutter member is engaged with said guide groove of said guide member such that said portion of said shutter member, which is engaged with said guide groove of said guide member, slides along said guide groove of said guide member.