Celticystis n. gen., a gomphocystitid from the Silurian of Sweden

Gomphocystites gotlandicus Angelin, 1878 is re-described on the basis of new material from Gotland, Sweden. It differs sufficiently from Gomphocystites s.s. to justify the erection of a new genus, Celticystis. The helmet-shaped Celticystis n.gen. has four circumoral plates forming the mouth frame, whereas Gomphocystites has seven. Celticystis n.gen. has adambulacral plates in the greater part of the theca and ambulacral flooring plates in the basal portion. The plate distribution in Celticystis n.gen. is more regular than in Gomphocystites, from which it is considered to be descended.