2 Art. 1.— M. Yokoyama : 



provinces lying to tlie east of it. The Mollusca and tlie Braclii- 

 opoda described in the present paper are those obtained ivom the 

 shell-layer of tlie latter. 



The position which this shell-layer occupies in the Upper 

 Musashino is not far from the overling loam, though at various 

 distances from it. AtOji, a northern suburb of Tokyo, where Brauns 

 and Tokunaga obtained a great deal of their materials,^ the shell- 

 layer is given by them as separted from loam by layers of clays, 

 sands and gravels which together make up a thickness of about 4,3 

 metres, and wliich, according to Tokunaga, grows to about 6,6 

 metres at Tabata, a place about 3 kilometres south-east of Oji, and 

 diminishes to about 2,5 metres at Shinagawa^\ a suburb at the 

 southern extremity of Tokyo. At Ötake, Shimosa, the interven- 

 ing layer is a sand about 3,6 metres in thickness, while at Shitr», 

 Kazusa, it is between 2 and 4 metres. From these we know that 

 the shell-la^^er occupies a position very near to the upper boundarj^ 

 of the Upper Musashino Formation. 



As to the thickness of the shell-layer itself, it is sometimes 

 considerable. At -' take and Takatano-Seki, it attains a thickness 

 of nearl}^ 7 metres in which shells are in such close heaps that the 

 layer is to a greater part made up of them. 



The loam and the underlying layers of the Upper Musashino 

 are generali}^ conformable with one another. But at Kido, Tega- 

 mura, on the south bank of Tega Swamp in Shimosa, the shell- 

 layer is superposed on a yellowish clay whose surface is full of deep 

 pits and holes, and this clay which is about 1,5 metres thick on an 

 average is again on a blue clay whose surface is very uneven. 



The localities from which the fossils have been collected are in 

 all six, viz. : 



1. Otake, Shimosa. ^^ Very near the railway station of Man- 

 zaki on tbe Abiko-Sawara line. 



1) I have been collecting- these fossils for more than 15 years, during- which time I was 

 assisted by several gentlemen among whom I may mention Messrs, N. Fuknchi, M. Öyu, T. 

 Og-ura, T. Matsumoto and S. Tsuboi, to whom my thanks are due. 



2. The shell-layer foruierly exposed at Oji, Tabata and Shinagawa is at presé^nt not acces- 

 sible for collection. 



3) Tmmm/\^n:kVr 



