468 Hayasaka — Richthofenia in Japan. 



On the whole, the section cnts through a Richthofenia 

 obliquely from the upper part of the opposite side of 

 the hinge line to a little below the hinge line. It was 

 only by chance that I was able to prepare such a thin 

 section from the limestone piece. 



Distribution of the Genus. — Richthofenia attracts 

 attention not only because of its peculiar form and shell 

 structure, but also because of its wide geographic distribu- 

 tion as contrasted with its limited time range. So far 

 as I know, the genus has been discovered in the following 

 places : 



1. Palermo, Sicily 9 Palaeo-dyas. 



2. Carnic Alps. 10 



3. Armenia 11 Permian. 



4. Salt Range, India 12 Permian. 



5. Lo-ping, prov. Kiang-hsi, China 13 . . .Upper Permian. 



6. Semenow Mountains, Nan-shan 14 . . . .Permian. 



7. Sutschan, near Wladiwostok 15 Schwagerina stage, 



8. Kobama, prov. Rikuzen (Kitakami 



mountainland) Lower Permian. 



9. Texas (Gaudalupe Mountains, etc.) 16 . Permian. 



Geological Age. — As to the geological age of the genus, 

 we must conclude, from what has been given in the above 

 list, that it is an important index fossil of the Permian, 

 although the detailed range in the Permian is as 

 yet to be determined. Detailed examination of all the 

 species described may throw some light upon the specific 

 differences and stratigraphical positions. 



Institute of Geology and Paleontology, 



Tohoku Imperial University, Sendai, Japan. 



9 Gemmellaro : La fauna dei calcari con Fusulina della valle del fiumo 

 Sosio (after Freeh, Lethaea palaeozoica). 



10 Schellwien : Die Fauna des karn. Fusulinenkalks, I. Palaeontogr., 39, 

 1892. 



11 Stoyanow : On Some Permian Brachiopods of Armenia, Mem. Com. 

 Geol., Nouv. ser., Ill, 1915. 



12 Waagen : op. cit. 



13 Kayser : Obercarb. Fauna von Loping, Kichthof en 's China, vol. IV, 

 1883. 



14 Schellwien : Palaeozoische u. Triadische Fossilien aus Ost-Asien, 

 Futterer 's Durch Asien, III. 



15 Tschernyschew : Die obercarb. Brachiopoden des Ural u. des Timan, 

 p. 731. 



16 Girty: The Guadalupian Fauna, 1908. 

 Bose: op. cit. 



