Conus (Conchlioconus) gradatus (Yokoyama, 1928)





Yokoyama (1928 : 338, pi. 66, figs. 3, 4) described and figured two specimens from the Pliocene of Japan as Cochlioconus gradatus gen. et sp. nov. The new genus was not explicitly referred to any family, but it was described as " Conus-like " and Yokoyama stated that " The presence of a deep sutural notch reminds us of the genus Conus." Pilsbry saw this paper and wrote to Yokoyama, drawing his attention to the similarity between Cochlioconus and Thatcheria. Yokoyama then stated in a subsequent paper (1930) that he regarded Thatcheria (T. mirabilis} and Cochlioconus (C. gradatus) as congeneric, though not conspecific, the Pliocene species being more Conus-like in appearance than the Recent form. He did not, however, change his views on the systematic position of the genus, for he wrote (p. 406) " I think I am right in placing it near Conus. This opinion seems to be also shared by Mr. Pilsbry as is evident from his communication." He also stated, probably wrongly, that Angas' specimen of T. mirabilis may be the only one now existing [i.e., in a collection] in the whole world."


Epoca: Pliocene




The University Museum, The University of Tokio


Conchlioconus gradatus (Yokoyama, 1928)

Thatcheria gradata (Yokoyama, 1930)

Thatcheria mirabilis (Makiyama, 1959)






         (1) - Yokoyama, M., 1928. Journal of the Faculty of Science, Tokyo Imperial University, sect. 2. vol. 2 (pt. 7 )