The Echinoid Directory

Family Arbaciidae Gray, 1855, p. 36

[Nomen correct. Gregory, 1900, p. 307 pro Arbaciadae Gray, 1855; = EchinocidaridaeTroschel, 1872, p. 293; = Coelopleuridae Markel, 1969, p. 24.]

Diagnosis	Carinacea with: apical disc flush and without perianal tubercles; dicyclic (rarely hemicyclic). Periproct with just 4-5 valve-like plates; ambulacra trigeminate (rarely quadrigeminate), with aboral pore-pairs lacking suckered disc and specialized for respiration (pore-pairs subconjugate); plate compounding in arbaciid style, with large central element bearing tubercle flanked by upper and lower demiplates; primary tubercles imperforate and non-crenulate; first coronal interambulacral plate present, often projecting interradially.
Range	Lower Cretaceous to Recent, worldwide.
Classification and/or Status	Euechinoidea, Carinacea, Echinacea, Arbacioida
Remarks	The family is distinguished from other Carinacea by its characteristic plate compounding. The following taxon may belong here but is currently too poorly known for firm placement: Progonechinus Duncan & Sladen, 1882 Gray, J. E. 1855. An arrangement of the families of Echinida, with descriptions of some new genea and species. Proceedings of the Zoological Society, London, 23, 35-39.