OKADAlßA SHELL MOUXD AT HITACHI. 



BY 



I. IIJIMA and C. SASAKI. 



GENERAL CHARACTERS OP THE OKADAIRA SHELL MOUND. 



Tlie Okadaira shell mound lies on the south western side of a hill called 

 Okadaira, and the eastern and western sides of it are already cultivated for 

 plantations. A white appearance due to broken shells which the ground possesses 

 in the vicinity of this hill is due to the remains of former mounds which have 

 been scattered and destroyed by the farmers. 



The length of this mound is estimated about eighteen ken (about 33 m.) in 

 length, and sixteen ken (about 29 m.) in width, and its surface is thickly covered 

 with a number of huge trees. The soil covering the mound is about six inches 

 in thickness. The height of this mound varies from a foot to seven feet. The 

 thickness of the deposit which varies from six inches to three feet, is in its deepest 

 parts about six feet. 



The mound itself , is nearly half a ri from the lake of Kasumigaura on the 

 north-eastern side, and also half a ri distant from a branch of the same lake on 

 the west. And furthermore it is distant about five ri (about 12.5 miles) from 

 the shore of the sea of Kashima (Pacific ocean) of Hitachi. 



The evidence that the lake was formerly washed by the ocean is shown by 

 ancient historical records of Hitachi (Hitachi Füdoki) and also from the presence 

 of fossil remains of marine shells at various exposures along the coast. 



SPECIAL CHARACTERS OF THE OKADAIRA DEPOSIT. 



The Okadaira Mound does not show any remarkable difference in its features 

 from those of the Omori mounds which are described by Prof. Edw. S. Morse in 

 the first memoir of the science department of the University of Tokio in 2539 

 (1879). As a general rule, objects obtained from such a deposit in both the 

 American and European Continents agree in their general aspect, but each 

 deposit has its special characteristics. 



