Stromatoporidae

Stromatoporidae, a group of extinct organisms of which the affinities have long been somewhat uncertain. There seems, however, to be little doubt that they are really Hydrozoa (q.v.), and allied to some such type as Hydractinia (q.v.). They form massive coral-like structures composed of calcareous layers concentrically arranged and separated by small vertical pillars. The group ranges from the Silurian to the Lias.