When Duncan & Sladen erected their genus Eolampas, they were either not aware of Pseudopygaulus or did not consider it a valid genus (Kier, 1962, p. 221). They later (1887) stated that Pseudopygaulus and Eolampas are synonymous, a view held by subsequent authors. However, controversy has remained over which name has priority.
The type species of Pseudopygaulus and Eolampas are very similar and certainly congeneric. Eolampas antecursor and E. excentricus have slightly narrower petals than the type species of Pseudopygaulus (P. trigeri Coquand). Such a character is not worthy of generic distinction.
Duncan, P. M. & & Sladen, W. P. 1882. A description of the fossil Echinoidea of western Sind. The fossil Echinoidea from the Ranikot series of nummulitic strata in western Sind. Memoirs of the Geological Survey of India, Palaeontologica Indica, series 14, 1, part 3, fascicule 2, pp. 21-100, pls 5-20.
P. M. Kier. 1962. Revision of the cassiduloid echinoids. Smithsonian Miscellaneous Collections 144, (3), 262 pp.