Editing Blastoid (section)

==Taxonomy==
{{See also|List of echinodermata orders}}
Blastoids are assumed to have evolved from the [[Cystoids]]. Blastoids are subdivided into two orders: [[Fissiculata]], which are characterized by direct entrance to the individual hydrospires by way of slits; and [[Spiraculata]], which are characterized by indirect entrance to the hydrospires through canals by way of pores. The earliest blastoid yet found, ''Macurdablastus'' from the Middle Ordovician of [[Tennessee]], cannot be classified as either order.