Probably ninety per cent of the American populace think the only Chinese food is the Cantonese. Happily this is not so, and such dishes as Peking ravioli, shrimp on toast, and Shanghai duck are delicious evidence that the Mandarin is just as good, if not better. Until now northern Chinese fare has been as rare in discovery as it is superb in taste, and local epicures have had to travel many miles in search of it.

But travel out, whether by rickshaw, Volks-wagen or the Belmont bus, to the Fresh Pond rotary and you will find Cambridge's own mecca for fanciers of Mandarin treats such as Moo Shi pork, and hot and sour Peking soup. A dish that particularly recommends itself is Joyce Chen special shrimp--a specialty of the house, of course, because it bears the name of the proprietor.

Mrs. Chen is a charming expatriate of Shanghai. She left her native city with her husband nine years ago to escape the Communist regime. Mrs. Chen explains that she decided last June to open a restaurant, "Because I like to cook and to give our northern Chinese friends a place to eat." And the restaurant does attract many Chinese, as well as a good proportion of the faculty and students engaged in Oriental studies at the University. Mrs. Chen should corner the market of Mandarin food-lovers in the whole Metropolitan Boston area. Indeed, all of Massachusetts, or all of New England, for it is the only one of its kind in the Northeast Corner.

The decor of Joyce Chen's shows an admirable lack of ostentation, and functions as a pleasant setting for a pleasant meal, not a flagrant melange of colors and quasi-Oriental art junk. "We decided that, even though we couldn't get real ornaments from Communist China, we wouldn't use the fake decorations of many Chinese restaurants," Mrs. Chen explains. "No dragons for us."

Satisfied customers agree about the inadvisability of paper dragons, give the traditional Chinese sign of appreciation for a good meal and depart.