Opinion 557 Designation under the Plenary Powers of a type species in harmony with accustomed usage for the nominal genus Calycoceras Hyatt, 1900 (Class Cephalopoda, Order Ammonoidea)
Published in Opinions and declarations rendered by the International Commission on Zoological Nomenclature, in 1959, in volume 20, issue 24, pages 265-276
Date published:1959-04-14