Albert Barnes Commentary Joshua 19:15

"and Kattath, and Nahalal, and Shimron, and Idalah, and Bethlehem: twelve cities with their villages." — Joshua 19:15 (ASV)

Twelve cities - Only five have been mentioned, and the names in the verses preceding are apparently not names of Zebulonite cities, but merely of points in or near the boundary line. It would therefore appear that seven names have disappeared from the text, and perhaps also the definition of the western frontier.