On the typological basis of Perisphinctes Waagen, 1869 and the leading modern ammonite superfamily Perisphinctoidea Steinmann, 1890

A re-examination of the type specimen of Ammonites biplex Sowerby, 1821 shows that the reasons previously given for rejecting this species as the type species of Perisphinctes, to be replaced by Amm. variocostatus Buckland, 1836 (Hemming, 1954), were unfounded. Fortunately, the replacement, based on a macroconch type, is a better representative of the genus than its originally validly designated microconch, Ammonites biplex. The decision in Opinion 303 (Hemming, 1954) is therefore a good one but arrived at for the wrong reasons. It should be left unchanged.