Acasta Leach, 1817

Carriol, René-Pierre, 2008, New genus and new species of Cirripedia (Chthamalidae, Tetraclitidae, Archaeobalanidae and Balanidae) from the Middle Miocene of the faluns of Touraine (France), Zootaxa 1675, pp. 31-48 : 44

Genus Acasta Leach, 1817

Type species: Acasta spongites ( Poli, 1791) by original designation.

Diagnosis (after Kolbasov, 1993): Basis deeply cupshaped, rarely flat, circular margin, often bearing small teeth; internal surface smooth, without six radial ribs. Wall plates usually with longitudinal, internal ribs; in some species, wall plates separated by splits or windows covered by delicate membrane. Carinolaterals developed normally. Some species Scutum with or without radial striae. Cirral armature variable, segments of anterior ramus of cirrus IV bearing hooks, or thorns, or lacking either.

Species included: Twenty-seven extant species have been retained in the genus by Kolbasov (1993). One species also has fossil representatives: A. spongites ( Poli, 1791) from the Pliocene of France ( De Alessandri 1907) and Italy ( Moroni 1952). There are seven extinct species: A. undulata Darwin, 1854 a (Upper Pliocene, England); A. hebertiana Millet, 1866 (Miocene and Redonien, Maine-et-Loire, France); A. muricata Seguenza, 1876 (Pliocene, Italy); A. fischeri Locard, 1877 (Miocene, Corsica, France); A. sarda De Alessandri, 1894 (Oligocene, Sicilia, Italy); A. formae De Alessandri, 1897 (Miocene, Italy); A. cf cyathus Darwin, 1854a from Miocene of Victoria, Australia ( Buckeridge 1985).

A. schafferi De Alessandri, 1910 cannot be retained in Acasta as the structure of the parietes does not agree with the diagnosis of the genus. It would appear that De Alessandri (1910) described older specimens, which have the exterior surface of the parietes destroyed, with furrows, remains of longitudinal tubes similar to those of Balanus perforatus .