The Carnarvonshire Railway was incorporated by an Act of July 29, 1862, with powers to construct a standard-gauge line from the Bangor & Carnarvon at Caernarvon [1958 spelling] to Portmadoc, a distance of 27¾ miles, but only the centre portion, from Penygroes to Afonwen, 11¾ miles, was built.
Source: wiktionary