ENCIRCLING CORAL REEF 31 



rial might be mentioned on the windward coast between Kahuku and 

 Kaneohe, of which the most important is at Kahana. There is also a 

 broad area of it at Waimanalo. 



East of Diamond head and Kaimuki the consolidated sand is very ex- 

 tensive, attaining the altitude of 100 feet and more. This has heretofore 

 been called an elevated coral reef; but it exhibits abundantly inclined 

 lamination of the sandy layers. The real reef appears at Niu and at the 

 fish pond at Maunakea. 



As of minor interest, it may be mentioned that the unconsolidated 

 coral sands constitute a hill fully 40 feet high near Makua, adjacent to 

 the railroad, which give forth the peculiar sounds meriting the title of 

 " barking sands." Both these and the exposures at Kaena point abound 

 in long tubular concretions standing vertically, which when unsupported 

 are accumulated like roots of trees. • At the latter locality I found skele- 

 tons of Hawaiians uncovered by the wind, and bones of a large sea bird. 



On the seashore, at several places, I found coniferous logs, with stumpy 

 roots and branches, which drifted from the Oregon coast. Some of them 

 were enveloped by soft barnacles. They indicate to us the possibility of 

 the transportation of hardy terrestrial mollusca and the seeds of plants 

 from remote regions. After the stranding of the logs the animals will 

 leave them, and finding the conditions of existence favorable, will mul- 

 tiply and assume new characters in accordance with the principles of 

 evolution. Such I understand to have been the origin of the diverse 

 Achatinellidae. Ever since the country has been settled these logs have 

 been noticed, some of them of immense size.* 



Pearl River Series 



The coral reefs and limestones are intimately associated with sedi- 

 mentary deposits and volcanic flows, partly ashes, often disintegrated. 

 The whole assemblage is really a terrane about 1,000 feet in thickness. 

 It is best developed about the Pearl River locks, and hence for conven- 

 ience it may be termed the Pearl River series. Probably this series of 

 deposits began in the Pliocene, and the older layers may be a base on 

 which the volcanic ejections commenced to accumulate. Some authors 

 think that extensive Tertiary deposits are necessary for the starting of 

 volcanic activity in every country. If so, parts of the Pearl River beds 

 will be found beneath Koolau and Kaala. This series is evidently to 

 be compared with the thick limestone deposits in the Fiji islands, sup- 

 posed by Doctor Alexander Agassiz to underlie the living coral reef of that 



*For a full description of the coral reefs of the Hawaiian islands, see A. Agassiz, Bulletin Mus. 

 Comp. Zoology, vol. xvii, no. 3, 1889. 



V— Bull. Geol. Soc. Am., Vol. 11, 1899 



