BANGOR, Me. — Two Americans on Friday pleaded not guilty to charges that they participated in a decade-long international smuggling operation that, according to federal officials, brought narwhal tusks — the long, tapered tooth that makes the elusive Arctic creature look a bit like a floating unicorn — into the United States.

Narwhal tusks, which are made of spiraling ivory and are as long as nine feet, are sold legally in some parts of the world, including Canada, and can fetch prices as high as $30,000. But in the United States, their trade is mostly prohibited by the Endangered Species Act of 1973 and the Marine Mammal Protection Act.

The defendants, Jay G. Conrad of Tennessee and Andrew J. Zarauskas of New Jersey, face four kinds of charges in a 29-count indictment filed in federal court here late last year: conspiracy, conspiracy to launder money, smuggling goods into the United States and money laundering. Two Canadians, whose names were redacted in the indictment, were also charged.

According to the indictment, the Canadians obtained the tusks in Canada and hid them in the false bottom of a customized utility trailer. The indictment says they smuggled the tusks across the border through Calais, Me., and used a FedEx in Bangor to send at least 50 shipments of the tusks to buyers like Mr. Conrad and Mr. Zarauskas.