b PAPERS FROM THE DEPARTMENT OF MARINE BIOLOGY. 



known for his studies upon the biology of the Barrier Reef, flows southward 

 with about three tributaries and has cut a deep ravine through a cleft in 

 the southern side of the ash-rim of the crater. There is still another stream, 

 which we name Haddon Brook, in honor of Dr. A. C. Haddon, of Cambridge 

 University, by whose intensive anthropological studies in the Murray Islands 

 the natives of this region are better known than are those of any other part 

 of Torres Straits. Haddon Brook rises on the easterly side of the central 

 cone and flows in a general southeasterly direction, cutting its way in a deep 

 canon through the volcanic ash. 



Lieutenant Frank A. Potts, of our expedition, paid special attention to 

 the geologic features of Maer Island and our statements have received the 

 benefit of his able criticism; moreover, the geological conclusions presented 

 herewith are in essential accord with those of Haddon, SoUas, and Cole in 

 Transactions of Royal Irish Academy, vol. 30, 1892-1896, pp. 419-476, pis. 

 22-25; also, as a matter of historical interest, one should read J. B. Jukes, 

 on the Voyage of the Fly, vol. i, chapters 8 and 13, London, 1847. 



The growth and development of the fringing coral reefs has been pro- 

 foundly influenced by the outflow of silt and sand from these brooks and from 

 the lava and ash slopes of the island, while in other places, as at the western 

 corner of the island, the reef-flat has been encroached upon by sand dunes 

 composed of wave-washed volcanic and calcareous fragments. Hence, if 

 we are to understand the conditions which have affected the history of the 

 reefs, we must take into account those of the land itself and of the ocean 

 currents which impinge upon the eastern shore and then sheer around the 

 northern and southern ends of the island. Wherever the water is agitated, 

 cool and free from an excess of silt, the reef-flat is wide and covered with living 

 corals, but wherever it is calm, hot, and depositing silt the reef-flat is narrow 

 and the corals deficient. Indeed, it was at Maer Island that the author 

 found that, generally speaking, the efi^ects of silt and of temperature are 

 coordinated; those corals which can withstand high temperature being also 

 those which are most resistant to the smothering eff^ects of silt. Thus, 

 certain forms thrive best in the heated shore-waters not only because they 

 can withstand the high temperature, but because they are not easily asphyxi- 

 ated by silt; and, conversely, corals which live in the cool waters of the 

 seaward regions of the reef-flats are the species which are easily smothered 

 by silt or killed by high temperature. 



Maer Island is completely surrounded by a recent coral reef which is 

 especially interesting because no hurricanes have been known in this region, 

 and thus the corals grow on uninterruptedly and without the periodic destruc- 

 tion of vast masses, such as occurs along the Great Barrier Reef south of 

 Cairns. In fact, along the entire windward shore of Maer Island one was 

 able to find only two small pieces of branching Porites which had apparently 

 been cast upon the beach. In contrast with the many large stranded coral 

 heads seen upon the shores of Pacific islands in regions subject to hurricanes, 



