Brightonicystis Paul, 1971

Genus Brightonicystis Paul, 1971

Type species: Brightonicystis gregaria Paul, 1971 , by original designation; from the Ashgill Shales (Hirnantian), Cumbria and W Yorkshire, UK .

Species included: Type species and Brightonicystis salmoensis ( Sheffield et al., 2018) .

Remarks.—Among holocystitid genera only Brightonicystis and Holocystites have their ambulacral facets developed over two to four oral and facetal plates. All other genera have the facets developed within a single facetal plate, except for Paulicystis Frest & Strimple in Frest et al., 2011, where the ambulacra were recumbent on the thecal surface and grew down the theca beyond the facetal circlet ( Table 1). Brightonicystis differs from Holocystites in having nine or more, not six orals and in having at least four food grooves (A, B, D, and E) that follow sutures between orals.

Emended diagnosis.—Holocystitids with five ambulacral facets on oral and facetal plates, oral frame composed of nine or more plates, with two in the B and D ambulacra not reaching the inner margin of the mouth, humatipores buried beneath smooth external surface with many tangential canals (emended from Paul 1971: 142).

Stratigraphic and geographic range.—Hirnantian, Upper Ordovician, of Anticosti Island ( Canada), northern England ( UK), and Kinnekulle ( Sweden).