Notes on Hyolithellus Billings, 1871. Class Pogonophora Johanson, 1937

The genus Hyolithellus Billings , 1871 is discussed, and it is demonstrated that the much disputed “operculum” (Discinella Hall, 1871) must be excluded from Hyolithellus. The “operculum” has possibly monoplacophoran affinity. Evidence indicates that Hyolithellus may well be referred to the class Pogonophora Johannson, 1937. The structure of the tubular skeleton in members of the Pogonophora is strikingly similar to that of Hyolithellus. X-ray fluorescence analysis of the tubes apparently also confirms the pogonophoran relationship and the exclusion of Discinella and its allies from Hyolithellus. Considering the early appearance of representatives of the Hemichordata (Lower Ordovician), it does not seem unreasonable to regard the Lower- and Middle Cambrian Hyolithellus as a close relative of the Hemichordata