In 1929 the Marine Biological Association began a survey of the River Tees Estuary, to study the various physical and chemical conditions and the types and distribution of animal and plant life. At the same time a tidal stream survey was carried out by the Hydrographic Department of the Admiralty. Later, for purposes of comparison, the scope of the enquiry was extended to a survey of the Kiver Tay, but on a less extensive scale.

IT has been shown by Reid (1930) that the salinity of the water retained in a sandy foreshoreat low tide may be considerablyhigher than that of , a stream of brackish water flowing over it. A few similar observations have been made on the salinity of the water held in the muddy foreshore of the estuary of the River Tees.The mud banks exposed at low tide are very soft and glutinous, and contain a high percentage of organic matter derived largely from sewage and industrial wastes with which the estuary is polluted.At low tide, a small hole, some 6 inches deep, was dug in the mud, about 3 feet from the water's edge, and the water which slowly percolated into it was removed in a pipette and filtered. A sample of estuary water was taken at the same time a few feet offshore and the salinity of both samples was determined. The results are shown in the following table, where the average salinity at high water near the estuary bottom at the, stations sampled is also given :- It seems probable that non-burrowing animals living in an estuary are. subjected to greater variations and to lower minimum values of salinity than are burrowing forms at the same distance from the sea. It has been observed that, both in the clean, sandy estuary of the Tay, and in the polluted, muddy estuary of the Tees, burrowing marine animals are, on the whole, relatively more abundant in the central part of the estuary than-

SUMMARY. Mammals.—The two indigenous species of Mammals are only found in the Wallaby Group, the Wallaby on both the large islands, the Rat, as far as is known, only on East Wallaby Island. The latter is probably, and the former certainly, subspecificailly distinct from the mainland species. Snakes.—The three species of snakes do not appear to differ from the mainland forms. At present two have been found only on West Wallaby Island and the third on East Wallaby Island. Lizards.—‐Four families are represented by some 19 species. The seven species of Geckonidæ iire only known from the Wallaby Group, the two species of Pygopodidæ only from West Wallaby Island, and the single species of Agamidæ from the Wallaby Islands and North Island. The Scincidæ are represented throughout the group, though we only met with the smaller species of Lygosoma outside the Wallaby Group; one of the larger forms, Egernia stokesi was, however, formerly plentiful on Rat Island. Froas.—Nothing is known no to the habitat of the two species recorded from the group. Birds.—of the 12 land‐birds recorded from the Abrolhos, four Kestrel, Robin, Song‐Lark, and Pipit) are certainly only casual visitors, five others (Rail, Crake, Kingfisher, Swallow, and White‐eye) are probably visitors From the mainland, though all but the Crake and Kingfisher have been known to breed; the remaining three are almost certainly residents. Of these, the Pigeon and the Quail are found in the Wallaby Group and on North Island, the Scrub‐Wren only on the Wallaby Islands. The two latter are subspecifically distinct from the mainland forms. Looking now of the different groups of islands we find that West Wallaby Islad has two snakes and two slow‐worms confined to it, East Wallaby Island has one snake and one rat confined to it, whilst the two Wallaby Islands possess subspecies of a wallaby and a bird peculiar to them. The Wallaby Islands, with North Island, possess also one lizard and two birds not found in the other groups, one of the birds being a subspecies peculiar to the group. This distribution strengly suggests that the whole land‐fauna of the group has been derived from the Wallaby Islands *. One of the chief features of the weather on the Abrolhos is the prevalence during the summer of “southerly busters,” estremely strong southerly winds. The presence of the two birds on North Island is thus easily accounted for, and it, is noteworthy that the one lizard which habitually climbs bushes is the one which has managed to reach that island. Doubtless at times the Lushes on the sand‐hills which it frequents are blown into the sea, and occasionally reach North Island. The fact that the smaller skinks are found on many of the small sandy islets seems to show that the sea is no great burrier to their distribution. Probably their eggs are not damaged by floating in sea‐water for some time. The larger Spiny‐tailed Skink, Egernia stokesi, is a favourite food of the Sea‐Eagles, and it is possible that individuals may be captured by them on the Wallaby Group and coppied to tha...

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