LISBON (AP).- Portuguese police say they have arrested two foreigners on suspicion of stealing rhino horns from a museum in central Portugal. The arrests came after a recent spate of rhino horn thefts from European museums this year. Authorities say the horns, purported to have aphrodisiac and medicinal qualities, are more valuable than gold on the black market. Thieves took a pair of horns from the Museum of Natural History at the University of Coimbra, in central Portugal, in April. Police said in a statement Monday they arrested a father and son, aged 63 and 31, as they attempted to fly out of Portugal last week allegedly with six rhino horns valued at euro400,000 ($565,000) in their luggage. Their names and nationalities were not immediately available.