Magnetic recording tape cassette

A magnetic recording tape cassette which comprises a bottom case half, a top case half mated with said bottom case half to form a cassette case having a front wall with a plurality of openings defined therein, a pair of guide pins provided near the respective front corners of said cassette case, means provided in each of said top case half and bottom case half for receiving screw fastening means for fastening said top case half to said bottom case half, a pair of reels accommodated within said cassette case for receiving a magnetic recording tape, said magnetic recording tape being adapted to be wound about said reels so as to pass along said plurality of openings defined in the front wall of said cassette case and along said pair of guide pins provided near the respective front corners of said cassette case, a protective lid member movably mounted on the front portion of said top case half so as to close or open said openings of said cassette case, said lid member including a horizontal upper plate and a vertical lid plate to form a reverse L configuration in cross-section, a pair of legs formed on each end of said horizontal plate extending perpendicular to the longitudinal direction of said horizontal plate, each of said legs being provided with a means for engaging with corresponding engaging means formed on the side walls of said top case half, said horizontal plate being placed on the frontmost portion of said top case half and a pair of openings defined in the rear edge of said horizontal plate juxtapositioned to each of said legs, each of said openings having an arcuate configuration which allows for the expansion of said legs of said lid member outwardly for engaging said leg engaging means with said corresponding side wall engaging means of said top case half.