WORTH NOTING ON TV

* SATURDAY

The Flagstones (The Cartoon Network, 8-10 p.m.): It may be of interest mainly to ``Flintstones'' fanatics, but the pilot of the hugely popular cartoon has been discovered and is to be aired for the first time. The family was called ``The Flagstones'' then, but the name conflicted with a newspaper comic strip and also didn't sound quite right - too suburbanish. The cartoon's creators - William Hanna and Joseph Barbera - tried ``Gladstones'' and a few other titles before coming up with ``The Flintstones,'' which became the show's name by the time of its primiere in 1960 as the first prime-time cartoon series made for television.

Fans will notice that a lot has changed since the pilot. And even before the pilot, Hanna and Barbera had fooled around with the idea of a family of Pilgrims, Eskimos, Romans, and cowboys before settling on the fur-clad characters known today. The rest may be pop history, but for those who missed some of the first 166 episodes, all of them will be aired in a mind-numbing marathon beginning at 1 p.m. on May 19 and running through midnight, May 22.

The Cartoon Network is spending the next two months, in fact, celebrating aspects of this influential animated series. This pilot should prove historically interesting in learning how the craze started. * SUNDAY

Roman City (PBS, 8-9 p.m.): Live action and high-quality animation - along with location shots - are all used to tell a story of Roman city-building around 27 BC in this unusual program. It is the fourth in a series of specials based on the fascinating and instructive books of David Macaulay, who provided their revealing illustrations along with the text. ``Pyramid,'' ``Castle,'' and ``Cathedral,'' all became programs.

``Roman City'' describes the planning, construction, and life of Verbonia, a city in Gaul. It is a fictional place, but its story combines historically accurate facts and details that offer a clear picture of the time.

As in the previous shows, Macaulay serves as host.

Please check local listings for these programs.