NEW SPECIES OF THE GENUS ACASTA (CIRRIPEDIA, THORACICA) FROM THE SOUTH WESTERN PART OF THE INDIAN-OCEAN

Four new species of the genus Acasta from the South-Western part of the Indian Ocean are described. Acasta pistulata is the most primitive of all. It has membraneous basis, lateral plates with small calcareous projections, and unarmed cirri. The apperture of the operculum is quite small. Radii are underdeveloped. It was found at a depth of 60 m in Spirastrella sp. A. planibasis has flat basis and the lateral plates with long calcareous thorns. Cirri of III and IV pairs have got some little thorns on the frontal surface of their segments. Basis has six longitudinal internal, ribs. It was found at a depth of 2 - 3.5 m in Dysidea sp. A. daedalusa has very deep basis without ribs and lateral plates with small rarely spaced projections. Scutum has bristles and longitudinal ribs. Found at a depth of 20-25 m, from Haliclona sp. A. collucata has specific lateral plates with two layers, the external layer is porous, radii are under-developed. Carinolateralia has rudimental medial part. Basis quadrangular. Found at a depth of 4 m. in Spongia sp.