^^^- ^- C. C. Yu — Ordovician Cephalopoda of Central China (ii) IS 



however, believes it is more likely of Lower Ordovician rather than Cambrian age. 

 Unfortunately, Mr. Shu and I also have not discovered, in our extensive journey in 

 northern Hupeh, any characteristic fauna other than the so-called Archxocyathus from 

 the basal part of Ichang formation, which could throw more light on this unsettled 

 question. 



The geological horizon of the Neichiashan formation has been considered by 

 many previous authors to be Middle Ordovician or lowest Upper Ordovician. Mr- 

 Shu and I obtained from the lower part of this formation just underlying the cephalopod- 

 bearing bed at Tai-hung-shan, 3 U west of Nan-chang district, many specimens of a well- 

 preserved characteristic graptolite, namely Didymograptus murchisoni Beck, which had 

 not been found by any former traveller in Hupeh province and its neighbouring 

 localities. From this characteristic graptolite we may readily conclude that 

 the lower part of the Neichiashan formation actually corresponds to the 

 Didymograptus murchisoni zone of the British Ordovician rocks, while the cephalopods 

 contained in the upper part of the formation and described in the present paper 

 show approximate equivalency to the Orthoceras limestone of Sweden and the 

 Vaginoceras limestone of the Baltic province of Russia. 



THE RELATIONSHIP BETWEEN THE ORDOVICIAN CEPHALOPODS FROM HUPEH, 



CENTRAL CHINA AND THOSE FROM THE CORRESPONDING HORIZON IN 



NORTHERN AS WELL AS SOUTHERN CHINA. 



Before comparing the cephalopod faunas of North and Central China, we must 

 summarize the distribution of the Ordovician cephalopods collected at various times 

 from the different localities in China. 



I. In Manchuria. 



a. From Hsiau-sorr, Fengtien, Richthofen collected the following form which 

 was described by Freeh' and referred by him to the Upper Ordovician. 

 Prof. Grabau, however, recognized that this bed is of the same horizon 

 as the Machiakou limestone in Chihli. 



Actinoceras richthofeni Freeh 



b. In the year 1928 T. Kobayashi described many Ordovician cephalo- 

 pods from Corea and South Manchuria. ^ Those collected from the Tofango 

 fossil bed at To-fan-go and Niu-shin-tai of Fengtien province are of the same 

 horizon as the Machiakou limestone. The species are as follows: 



1. F. Freeh: In Richthofen's China, Vol. V, p. 8. 



2. T. Kobayashi: Ordovician Fossils from Corea and South Manchuria. Japanese Journal of 

 Geology and Geography, Vol V, No. 4. 



