Haeckel, 1879
Diagnosis
Siliceous skeleton bivalved, of two mirror-image halves, simple or with elaborate structures of branching radial spines.
Although both families placed in this order are basically bivalvar, the valves of the Coelodendridae are spatially insignificant and structurally unlike the regularly latticed valves of the Concharidae. It seems likely that they should be placed in separate orders.
Families treated:
Family Coelodendridae Haeckel, 1862
Family Concharidae Haeckel, 1879