Tape cassette having ribs and window

A tape cassette comprising:

• a cassette casing composed of an upper half casing and a lower half casing, each formed of a flat surface wall portion and an outer peripheral wall portion, the outer peripheral wall portion of each of said upper and lower half casings cooperating to define finger touch portions protruding from the outer peripheral wall portions,
• a pair of hubs around which a tape is wound and which are rotatably fitted into openings defined by circular peripheral wall portions projected from an inner surface of the flat surface wall portion of one of said cassette half casings,
• tape guide members formed in the cassette casing at positions through which the tape wound around the hubs is traveled,
• wherein the thickness of the flat surface wall portion and the thickness of the outer peripheral wall portion of the upper and lower half casings, including said finger touch portions, are uniform,
• a plurality of parallel linear ribs projected from the inner surface of the one of the half casings in the vicinity of the circular peripheral wall portions, said linear ribs including a center rib contiguous with said circular peripheral wall portions and extending on a line extending through centers of the openings defined by the circular peripheral wall portions, said linear ribs further including at least one pair of side ribs, each side rib disposed at an opposite side of said center rib and spaced therefrom at a predetermined distance to define spacings between said ribs, and
• elongate windows formed in said flat surface wall portion of said one of said cassette half casings at locations limited to said spacings between said side ribs and said center rib so that said center rib is continuous between said circular peripheral wall portions.