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Family  Scaliolidae

The Scaliolidae is a small family of small or minute molluscs that occur throughout the tropical and subtropical Indo-West pacific. There are perhaps 25 named species, but they are so poorly known that this can only be a rough estimate.

The family contains only two genera, Finella and Scaliola. Scaliola is unusual in that it attaches sand grains to its shell, in the style of the larger Xenophoridae. They live in the lower littoral and sublittoral, feeding on detritus.

The family is well-defined anatomically due to the work of Ponder (1994) who described the shell, radula, external characteristics and anatomy of one species of Finella and one species of Scaliola from Hong Kong. The animals have an extremely extensible snout, in the case of Scaliola being able to reach onto the dorsal surface of the shell to gather food. Sexes are separate, producing planktotrophic larve, giving rise to a multiwhorl protoconch with a deep sinusigeral notch.

The state of knowledge of this family is so poor that it is difficult to itemise the NSW species. In the Australian Museum collection there are many hundreds, perhaps thousands, of specimens assigned to the family but they are not identified to species, except for Finella pupoides. This species is widely distributed in the Indo-West Pacific, reaching as far south as Sydney, where it is moderately common in estuaries. Another unnamed species of Scaliola is recognised from NSW estuaries. There is a further species of Finella described from NSW (listed in Coverage below) that is known only from the type specimens, although there are probably additional specimens among the Museum's unsorted material. Iredale & McMichael (1962) also listed Scaliola caledonica Crosse, 1970, described from New Caledonica, as occurring in NSW, but there are no specimens sorted out in the Museum collection.

Family reference

Ponder, W.F. (1994). The anatomy and relationships of Finella and Scaliola (Caenogastropoda: Cerithioidea: Scalioidae). pp. 215-241 in Morton, B. (ed.) The Malacofauna of Hong Kong and Southern China III. Hong Kong. Hong Kong University Press: Hong Kong.

Coverage

In addition to the figured species, there is another species described from NSW but known only from type specimens:

       Finella jacksonensis (Laseron, 1950) Type locality: Off North Head, Sydney, NSW.

Identification Notes

In NSW, shells in this family are small (less than 4 mm), elongate without varices, and the aperture is without an anterior canal. Species of Scaliola are easily recognised by the attached sand grains. The protoconch is of 2-4 whorls, and terminates with a sinusigeral notch, with a strong varix on the upper half of the whorl (Fig. 1, from Ponder (1994)). Unfortunately, specimens with an intact protoconch are uncommon.