New and little-known species of Didemnidae (Ascidiacea, Tunicata) from Australia (Part 3) Author Kott, Patricia text Journal of Natural History 2005 2005-06-30 39 26 2409 2479 http://dx.doi.org/10.1080/00222930500087077 journal article 10.1080/00222930500087077 1464-5262 5215680 Polysyncraton orbiculum Kott, 1962 ( Figure 15B ) Polysyncraton orbiculum Kott 1962 , p 300 and synonymy; 2001, p 117. Distribution Previously recorded (see Kott 2001 ): Western Australia ( Rottnest I. ); South Australia ( Gulf St Vincent ); Victoria ( Western Port ). New record: SW Australia ( Mason Bay , 33 ° 57940S, 120 ° 289100E, WAM 128.90 ) . Description The newly recorded colonies are small (less than 1 cm ) irregular plates on weed. The characteristic blister-like vesicles surround each stellate branchial aperture on the surface of the colony. Spicules also are characteristic, to 0.05 mm diameter, with 9–11 short, crowded, conical to round-tipped rays in optical transverse section. The zooids are immature. Remarks Although these colonies are immature, the circle of vesicles around each branchial aperture and the spicules with their short, crowded rays are characteristic of this temperate species, which so far is known from only relatively few records.