Dusttight tape cassette

A tape cassette comprising:

• a cassette case comprising a main cassette body having a front opening at the front thereof and a lid rotatably mounted on said main cassette body for normally covering said front opening, said main cassette body comprising a top plate, a bottom plate, a rear plate, and right and left side plates, said top and bottom plates each having a linear front edge at said front opening and having no cutout part at said front opening;
• and
• a sliding body slidably provided within said main cassette body so that a part of said sliding body is extractable through said front opening for supporting a pair of tape rolls of a magnetic tape, said sliding body comprising guide parts for guiding the magnetic tape between said pair of tape rolls along the front of said sliding body and a cutout part through which the magnetic tape along said front of said sliding body traverses,
• when said tape cassette is not in use said sliding body being completely accommodated within said main cassette body and said cutout part being covered by the bottom plate of said main cassette body,
• when said tape cassette is in use and is loaded into a magnetic recording and reproducing apparatus said lid opening and a part of said sliding body being extracted through said front opening so that said cutout part is exposed outside said main cassette body to permit tape draw-out means of said apparatus to enter into said cutout part.