What's the plural of Prius?

International Herald Tribune has a fun article trying to figure out how to refer to multiple Prius vehicles. It could be Priora because Prius is a "neuter nominative/accusative singular of the adjective prior." It could also be Prioria because "adjectives of the third declension belong to the i-stem declension" (Don't ask me to explain that). Priora means the car is masculine or feminine but if cars are women, then it's Priores. Other candidates include Prii, Prix and Priapic. I think I will stick with Priuses.

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[Source: International Herald Tribune]