The blastoid genus Phaenoschisma Etheridge and Carpenter, 1882, is redefined on the basis of its type species, P. acutum (Sowerby), using exposure of hydrospire slits as a chief criterion. Of six other species originally assigned, P. archiaci is now type species of Deltaschisma Fay, 1961, and P. caryophyllatum is type species of Phaenoblastus Fay, 1961; the others do not belong to Phaenoschisma and require restudy. Conoschisma Fay, 1961, type species C. laeviculum (Rowley), is a junior synonym of Phaenoschisma. Phaenoblastus conicus Fay is reassigned to Phaenoschisma. Three species of Codaster are assigned as Phaenoschisma gracillumum, P. pecki, and P. chouteaui. Phaenoschisma now contains six species, in the Kinderhookian of Missouri, Osagean of Illinois, Missouri, New Mexico, and Iowa(?), and equivalent Visean strata in England.

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