The wandering Worms (Polychaeta errantia) are also recognised by their impressions, trails, borings and castings. Burrows formed by these worms are seen in _Arenicolites_, found in the Silurian sandstone of New South Wales, near Yass, and in the Carbopermian (Gympie Series) near Rockhampton, Queensland. The membranous-lined burrows of _Trachyderma_ (_T. crassituba_), occur in some abundance in the Silurian mudstones in the neighbourhood of Melbourne, Victoria (Fig. 82 A). The genus _Trachyderma_ is common also to Great Britain and Burmah, in beds of the same age. =Worm Tracks.--= Some of the curious markings on the Carboniferous sandstone of Mansfield, Victoria, may be due to worm trails and castings, especially since they are associated with sun-cracks and ripple-marks. =Sedentary Worms.--= The sedentary or tube-making Worms (Polychaeta tubicola) are represented by numerous forms. The long conical tube of _Cornulites tasmanicus_ is recorded from the Silurian of Zeehan, Tasmania (Fig. 82 B). _Spirorbis_ occurs in the Middle Devonian of Victoria (Fig. 82 C), and W. Australia, and also in the Carbopermian of W. Australia. _Torlessia_ is found in the Trias or Lower Jurassic of the province of Canterbury, New Zealand (Fig. 82 D). The genus _Serpula_ is widely distributed, occurring in the Carbopermian (Upper Jurassic Series), near East Maitland, New South Wales (_S. testatrix_), in the Jurassic of W. Australia (_S. conformis_), in the Lower Cretaceous of Wollumbilla, Queensland (_S. intestinalis_), and the Darling River, north west of New South Wales, (_S. subtrachinus_), as well as in Cainozoic deposits in Victoria (_S. ouyenensis_). _Ditrupa_ is very abundant in some shelly deposits of Janjukian age in Victoria. MOLLUSCOIDEA. The Sea-mats (Polyzoa) and the Lamp-shells (Brachiopoda) constitute a natural group, the MOLLUSCOIDEA, which, although unlike in outward form, have several physiological structures in common. The respiratory organs lie in front of the mouth, and are in the form of fleshy tentacles or spiral appendages. These animals are more nearly allied to the worms than to the molluscs. _POLYZOA._ =Characters of Polyzoa.--= These are almost exclusively marine forms, and are important as fossils. They form colonies (polypary or zoarium), and by their branching, foliaceous or tufty growth resemble sea-weeds. The cells in which the separate zoöids lived have peculiar characters of their own, which serve to distinguish the different genera. =Subdivisions of Polyzoa.--=