Assets of the nation's 513 money market mutual funds fell $444.9 million in the latest week, the Investment Company Institute said Thursday. The decline, to $384.99 billion in the seven-day period ended Wednesday, followed a revised $1.32 billion increase in the funds' assets the previous week, according to the Washington-based mutual fund trade group. The previous week's increase originally was reported as $988.6 million. The funds' assets hit a record high $392.14 billion in the week ended March 21, 1990. The Investment Company Institute said that in the latest week, assets of 250 general purpose funds rose $27.7 million to $133.99 billion, assets of 102 broker-dealer funds dropped $356.4 million to $159.17 billion, and assets of 161 institutional funds declined $116.2 million to $91.83 billion. The seven-day average yield on money market mutual funds was 7.67 percent in the week ended Tuesday, unchanged from the previous week, according to Donoghue's Money Fund Report, a trade journal based in Holliston, Mass. The 30-day average yield also was unchanged at 7.67 percent, Donoghue's said. The average maturity of the portfolios held by money funds was 44 days, unchanged from the previous week, Donoghue's said. Separately, the newsletter Bank Rate Monitor said its survey of 100 leading commercial banks, savings and loan associations and savings banks in the nation's 10 largest markets showed the effective annual yield available on money market accounts was 6.18 percent as of Wednesday, unchanged from a week earlier. The North Palm Beach, Fla.-based newsletter said the effective annual yield available on special savings accounts, called Super NOW accounts, also was unchanged, at 5.04 percent. Bank Rate Monitor said the effective annual yield was 7.91 percent on six-month certificates of deposit, unchanged from the previous week. Yields were 8.10 percent on 1-year CDs, unchanged; 8.10 percent on 2{-year CDs, unchanged; and 8.17 percent on 5-year CDs, unchanged.