To avoid confusions related to the resurrection of Adenocephalus Nybelin, 1931 (Cestoda: Diphyllobothriidea), the type material of the Pacific broad tapeworm, Adenocephalus pacificus Nybelin, 1931, which also infects humans, is morphologically characterized. Transverse protuberances on the ventral side of proglottids anterior to gonopores, which are a diagnostic feature of the genus, are illustrated for the first time. The present study supports the importance of a study of type material even in the ‘molecular era’ of taxonomy, where the value of morphology is often underestimated. It also points out the need for specimen deposition in publicly accessible collections.