I am so proud of Congo. He never forgets anything,"" says the little elephant's mother Nyasa. But his wise grandmother Manyara only answers, ""That's very good. If he remembers what's important."" Congo's mental record of some of the things that are important--lions, food, manners--allows Manyara to slip some elephant information very smoothly and unobtrusively into her story. And there's another kind of lesson coming up: when older brother Zambesi ""forgets the rules"" and plays too rough, a toppled Congo vows ""I never, never forget."" For a miserably long time he doesn't, until Manyara reminds him, ""It is important to remember that you and Zambesi are brothers""--and Congo, forgiving at last, declares, ""I have a super memory. And I will always remember what to forget."" If all this seems a bit strung out for an easy reader, one has to admire the way McNulty weaves all the elements together, calling attention to none and ending up with a more than usually rounded composite. Simont's pictures are soft and agreeable; and he outdoes himself with the expressions of the dowager Manyara.