Based on Agassiz`s original drawings Durham (1955) reconstructed the oral plating of this genus and identified the periproct as opening between the fourth and fifth pairs of post-basicoronal plates. However, material illustrated by Mortensen (1948; see above) clearly shows the periproct to open between the first and second post-basicoronal plates, with the first pair extremely elongate. If Mortensen is correct in his species identification, then Hupea is identical in plating to Jacksonaster Lambert & Thiery, 1914. Durham`s plating diagram fits with Agassiz`s original drawing being of Peronella lesueuri (Agassiz), the only taxon know to have the periproct opening posterior to the first two pairs of post-basicoronal plates.
H. decagonale differs from the type species of Jacksonaster, J. depressum most obviously in having a flatter test with sharper ambitus and shorter petals but is otherwise identical in oral plating. It differs from Laganum in having elongate first post-basicoronal plates and a more marginal periproct.
Pomel, A. 1883. Classification méthodique et genera des Échinides vivante et fossiles. Thèses présentées a la Faculté des Sciences de Paris pour obtenir le Grade de Docteur ès Sciences Naturelles, 503, 131 pp. Aldolphe Jourdan, Alger.
Mortensen, T. 1948. A Monograph of the Echinoidea IV.2 Clypeasteroida. C. A. Reitzel, Copenhagen.
J. W. Durham 1955 Classification of clypeasteroid echinoids. University of California Publications in Geological Sciences 31, 73-192.