Marans are lower riding, straighter and longer in the back, with lower tail set, and have a "mahogany bay" eye.
Typical Blue Marans (pulled from Feathersite http://www.feathersite.com/Poultry/CGK/Marans/BRKMarans.html)
Langshan (note taller leg and "U")...that is the American standard "Croad Langshan." again from the Feathersite: http://www.feathersite.com/Poultry/CGK/Langshan/BRKLangshan.html
Edited by Lady of McCamley - 2/8/16 at 9:59pm