Every Part (19)

The Act of Union 1536 continues from post (18)...

"...and every part thereof, shall stand and be from and after the said Feast of All-Saints guildable, and shall be reputed accepted named and taken as parts and members of the said shire of Monmouth; and that the said town of Monmouth shall be named accepted reputed used had and taken head and shire town of the said county or shire of Monmouth; and that the sheriff's county or shire court of and for the said shire and county of Monmouth shall be holden and kept one time at the said town of Monmouth, and the next time at the town of Newport in the same county or shire, and so to be kept in the same two towns alternis vicibus and according to the laws of this realm of England for ever, and in none other places."

My translation of "alternis"= alternating, and "vicibus"= villages (towns).  Any folks out there have a precise definition?