MUSEUM OF COMPARATIVE ZOOLOGY. 147 



distribution of coral reefs, and of the streams of the islands of Oahu, 

 Maui, and Hawaii, clearly shows this interdependence (Plate I.), the coral 

 reefs being most prominent on the lee side. Combining with this .the 

 eflFect of the prevailing currents in bringing pelagic food to the growing 

 reefs, we have a most natural explanation for the absence of coral reefs 

 to the leeward of Hawaii, while the influence of the flood of fresh water 

 readily explains their absence along those parts of the shores of Maui, of 

 Oahu, of Hawaii, of Molokai, where they are not indicated on the map. 

 With the exception of a few patches of Pocillopora near Hilo, to the south 

 of the harbor, and on the west face of the island near Kawaihae and 

 Upolu, there are no corals to be found. In fact, we can hardly conceive 

 of a less favorable shore for coral reefs than the east face of Hawaii, where 

 from Hilo north there are in a length of about ninety miles over a hun- 

 dred water-flills, many falling perpendicularly into the sea from great 

 height, or pouring in rapid torrents down the steep banks and canons of 

 the eastern shore.^ Just as little could we expect, and for the same 

 reason, coral reefs to thrive on western Maui. Except at the junction of 

 the two parts of this island, we find now^heie conditions favorable for the 

 growth of coral reefs (Plate III.). 



The coral formation of Kauai, which extends as a narrow growing reef 

 on the eastern and windward shore, has been described by Dana. He 

 has also given an accoiuit of the solidified beach deposits ^ similar to the 

 drift sand rocks of Oahu, and has figured a solidified beach deposit 

 occtirring along the shores of the Koloa district, the remnant of a narrow 

 frino-inu- reef, which seems to run more or less continuously along the 

 whole eastern sea face of the island. 



Brigham^ is of the opinion that the reef near Koolaii (Kauai) has 

 been elevated. He also says* that ten or twelve miles west of Waimea 

 the coral reef has been elevated on a long wide ridge transversely to 

 the pi'esent shore line. Xear Lapa he speaks of a very curious sand- 

 bank, nearly sixty feet in height, formed by the winds and currents. 



1 Dana does not consider that fresh water has a great influence in the formation 

 of harbors in coral areas, but it undoubtedly at low stages of the tide increases 

 the volume of water which scours the harbors, while the detritus it carries must 

 prevent corals from growing along its course, even if the fresh water was not itself 

 a check to the growth of coral. Though corals in many instances are known to 

 live close to fresh water, yet the fact remains that they do not thrive along coasts 

 where large bodies of water empty into the sea. 



2 Dana, U. S. Expl. Expedition, Geol. "Report, pp. 275-277. 



3 Erigham, W. T., On the Volcanic Phenomena of the Hawaiian Islands, p. 344, 

 Mem. Bost. Soc. Nat. Hist., I., Part III., 1868. 



* Ibid., p. 349. 



