The third PlayStation volume contains Galaxian (1979), Dig Dug (1982), Pac-Man sequel Ms. Pac-Man (1981), Pole Position II (1983), The Tower of Druaga (1984) and Phozon (1983). The first four were well-known in the U.S., but the latter two were relatively unknown. It contained the now-customary museum mode. Two unique versions of The Tower of Druaga were also hidden in this volume. One called "Another Tower", and the other called "Darkness Tower". Both are harder than the original and require different methods to beat the game.
Source: Wikipedia, "http://en.wikipedia.org/wiki/Namco_Museum%23Namco_Museum_Volume_3Title," available under the CC-BY-SA License.