The Newest variety in the UK standard the Butterfly, is so called after the Caudal fin that is well divided and shaped like open wings of a butterfly when viewed from above. Its other characteristic is the predominant telescope eyes which are spherical in a raised sleeved socket,  and noticeably different from other telescoped eyed goldfish varieties.   

Unique in the UK Standard this is the first variety not historically breed for the show bench in the UK (before the ratification of the Nationwide Goldfish Standard in 2016) to be added to the Standards book. And as such this is the only variety thus far to pass a 5 year breeding protocol stipulated by the delegates of the Nationwide: Goldfish Societies UK and the only new variety since the Ryukin.  

Butterfly Standard