All along the shore were numbers of boulders which had been perforated through and through by the little Isopod crustacean Sphæroma, assisted here and there by a boring mollusc. These little creatures form a very powerful factor in the disintegration of the rocks, as, after they have driven their galleries through, it is quite an easy matter for the sea to do the rest. As commensals in the burrows of these Isopods, I have observed many other small crustaceans, several species of small fishes, including the Common Eel (Anguilla australis), and also a brown-coloured Araneid. This last—of which individuals were numerous—remains in the burrows even when the tide rises and floods them, and it may be seen moving about beneath the surface clothed in a tunic of air-bubbles.
While speaking of the seashore, I must mention something connected therewith which at once claims the naturalist's attention, and that is the zones which each animal (or set of animals) occupies. Taking a typical flat, and starting from the top, we would first come to a sandy zone, slightly above high water. This is inhabited by the beautiful "Swift-footed Crab" (Ocypoda cordimana), a small grey Isopod; and, in the event of there being decaying animal or vegetable matter, many specimens of the Common Sandhopper (Talorchestia quadrimana). Then, lower down, there is a zone just lapped at high water, about which are strewn clean stones (i.e. stones not overgrown with Algæ). Under these stones are to be found many interesting and exceedingly agile Crabs (Cyclograpsus Lavauxi). Going still lower, we come to a belt consisting of a mixture of sand and mud. On—or rather in—this we find the bright-coloured, martial-looking "Soldier Crab" (Mycteris longicarpus),[1] and an exceedingly fragile Callianassa. Going beyond this again, we arrive at a zone which is only just above low-tide mark. This is composed of dark evil-smelling mud, with occasionally small Algæ-covered boulders strewn sparsely over its surface. On the stones themselves (amongst the Algæ) we find some tiny Crabs (Hymenosoma varium and Porcellana dispar). Underneath will be found others and larger species, viz. Chasmagnathus lævis, Sesarma erythrodactyla, and occasionally Pilumnopeus serratifrons. In the mud
- ↑ For further information regarding these crustaceans, cf. author's "Notes on the Habits of some of the Australian Malacostracous Crustacea" (Zool. May, 1898).
