thr president.Last Rites Held ForClayton Mother And Her Seven Childrenthe church and another 150 waited outside in a drizzling rain.TCLAYTON, lAP) A mother and her seven children, victims ! of an early-morning fire that leveled their home Friday, were buried yesterday in a mass grave in St. Lawrence cemetery.Clifford Conant. 39-year- oid husband and father collapsed from grief twice.A 13-year-old daughter, Susan, the only other survivor of the fire, wept as she left the church.A gray steel casket, containing the body of Mrs. Conant, 29, and her year-old daughter, Nancy Anne, was flanked by six small, white caskets during the services at the Methodist church in this St. Lawrence river village.More than 400 persons were in