New Ordovician Bothriocidaridae from Girvan and a reinterpretation of Bothriocidaris Eichwald

Five specimens of bothriocidarid sea urchins are described; one is the seventh known example of B. globulus Eichwald. The other four represent Neobothriocidaris gen. nov. characterized by having perforate plates arranged in rows and one pore of each pore-pair shared by two plates. N. peculiaris and N. minor spp. nov. are separated on the number and arrangement of spine mamela. The holotype of N. peculiaris has parts of two radial water vessels preserved within the single columns of imperforate plates which have been regarded as inter-radial in Bothriocidaris. On the assumption that Neobothriocidaris and Bothriocidaris are closely related genetically, the single columns of imperforate plates in the latter are reinterpreted as being radial. The five apical plates become genitals with one modified as a madreporite. Growth of the corona is more readily explained and the entire columns of imperforate plates may represent oculars. Details of the peristome and jaw apparatus do not however fit the new interpretation very well.