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.—
Polyzoa are divided into the Sub-classes Phylactolaemata, in which the mouth of the zoöid has a lip, and the series of tentacles is horse-shoe shaped; and the Gymnolaemata, in which there is no lip to the mouth, and the tentacles form a complete circle. The first group forms its polypary of soft or horny material, which is not preserved fossil. The latter has a calcareous polypary, and is of much importance as a fossil group. This latter sub-class is further subdivided into the following Orders, viz.:—Trepostomata (“turned mouths”), Cryptostomata (“hidden mouths”), Cyclostomata (“round mouths”), and Cheilostomata (“lip mouths” furnished with a moveable operculum).
Trepostomata (Palaeozoic).—
The Order Trepostomata may include some genera as Monticulipora and Fistulipora, previously referred to under the corals. They become extinct after Permian times. Fistulipora occurs in certain Gippsland limestones.