10 BULLETIN 164, UNITED STATES NATIONAL MUSEUM 



each geological series and divides what he calls the Ordovician into 

 a middle division, designated as the Aigawa series, and a lower sub- 

 division, named the Chiaomaishan series. 



So far as I can judge from his description, his Chiaomaishan se- 

 ries belongs to the Ozarkian, while his Aigawa formation apparently 

 corresponds to the Middle Ordovician Ssuyen and Lower Ordovician 

 Wuting formations. 



GEOLOGICAL NOMENCLATURE 



Since I have found many characteristic Black River, Upper 

 Chazyan (Blount), Stones River, and Upper Canadian fossils in the 

 South Manchurian beds formerly called simply Ordovician, it be- 

 comes necessary to subdivide the series into four distinct formations, 

 for which I propose the names Ssuyen, Wuting, Kangyao, and San- 

 tao. It is likely that the Ssuyen formation may correspond to the 

 middle and upper parts of Kobayashi's Toufangkou series — that is, 

 it includes his nodular (X) and banded limestones (IX). Unfor- 

 tunately, since detailed descriptions of the lithologic characters are 

 not given in Kobayashi's 1930 paper, I can not determine the exact 

 relations between his Wolung series and my Wuting, Kangyao, and 

 Santao formations, but, so far as I can now tell, my three formations 

 apparently correspond to the lower part of Kobayashi's Toufangkou 

 and part of the AVolung series. 



Kobayashi (1930) studied also the Middle Ordovician strata de- 

 veloped at Bantatsu hill, 5 kilometers east of Heijo, Korea, and sum- 

 marized the sequence as follows, in descending order : 



Group I. (Nanso bed) — Gray coloured, more or less crystalline lime- 

 stone. Thickness about 50-70 m. 



Group II. (Unkaku bed) — Fossiliferous limestone with irregular gray 



dolomitic patches in black matrix. Thickness about 60 m. 



Group III. (Bantatsusan bed) — Alternation of dark gray massive lime- 

 stone and bluish gray thinly bedded limestone. Thickness about— 200 m. 



Group IV. (Kosei bed) — Alternation of gray marly slates and bluish 

 white, sometimes crystalline limestone. 



According to his explanation, the Unkaku and Bantatsuan beds are 

 exactly contemporaneous with his Toufangkou limestone. 



In a later chapter of this paper I discuss, in detail, the correla- 

 tions of the formations in Manchuria, China proper, Korea, and 

 North America; hence this matter need not be considered further 

 here. 



In the accompanying chart (p. 11) the views of the various authors 

 referred to in the preceding pages are tabulated, in order to facilitate 

 a clear understanding of the stratigraphic nomenclature involved. 



