The Echinoid Directory

Archiacia L. Agassiz, in Agassiz & Desor, 1847, p. 159

Diagnostic Features	Test of medium size, elongate, adapically high, in the type species very inflated anteriorly, with pointed prominence overhanging anterior margin; oral surface weakly depressed towards peristome. Apical system tetrabasal, very eccentric anteriorly, elongate, oculars II and IV usually in contact. Petals slightly developed, anterior petals (II & IV) curving posteriorly and shorter than posterior petals. Pores conjugate, inner pores circular, outer pores slit-like. Ambulacral plates beyond petals with pore-pairs Ambulacrum III non-petaloid, often in a groove; pore-pairs forming a double series of pore-pairs on each side. Periproct inframarginal, longitudinal, flush. Peristome pentagonal; subcentral to anterior. Bourrelets absent; a few small tubercles rimming the peristome. Phyllodes double pored with many pairs of pores in three series in each half ambulacrum. No buccal pores. Tubercles slightly larger adorally than adapically. Narrow naked zone in interambulacrum 5 behind peristome.
Distribution	Cretaceous (Cenomanian) of North Africa.
Name gender	feminine
Type	Archiacia sandalina L. Agassiz, in Agassiz & Desor, 1847, p. 159; by subsequent designation of d'Orbigny, 1856, p. 284.
Species Included	A. acuta Gauthier, in Thomas & Gauthier, 1889; Cenomanian, Tunisia. A. sandalina L. Agassiz, in Agassiz & Desor, 1847; Cenomanian, Tunisia, Algeria. A. palmata Gauthier, in Thomas & Gauthier, 1889; Cenomanian, Tunisia.
Classification and/or Status	Irregularia; stem group Neognathostomata; Archiaciidae.
Remarks	Archiacia is very similar to Claviaster, both genera having inflated tests, with a high, drawn-out cylindrical prominence overhanging the anterior margin, double pored phyllodes and a non-petaloid ambulacrum III. These genera differ in that ambulacrum III of Archiacia has a double series of double pores, while ambulacrum III in Claviaster has a single series of double pores. Szorenyi (1955, text-fig. 26) shows single pores in ambulacrum III of Archiacia hungarica. Kier (1962, p. 154) reports that all the specimens of Archiacia he has seen have the pores paired, and suspects that Szorenyi\'s drawings are not accurate. Agassiz, L. & Desor, E. 1846-1847. Catalogue raisonné des familles, des genres, et des espèces de la classe des échinodermes. Annales des Sciences Naturelles, Troisième Série, Zoologie: 6 (1846), 305-374, pls 15-16; 7 (1847), 129-168; 8 (1847), 5-35, 355-380. P. M. Kier. 1962. Revision of the cassiduloid echinoids. Smithsonian Miscellaneous Collections, 144 (3) 262 pp. E. Szorenyi. 1955. Echinides Cretaces de la Bakony. Geologica Hungarica, series Palaeontologica, 26, 268 pp., 22 pls.