Notices of Memoirs — Japanese Cretaceous Cephalo^Jocla. 413- 

 InTOTICIES OIF nVCIEJivdIOIE-S, lETO. 



I. — Cretaceous Cephalopoda from the HokkaidS. Part I : 



LVTOCERAS, GauDRYCERAS, AND TeTRAGONITES. By HiSAKATSU 



Yabe, Geological Institute, Science College, Imperial University, 

 Tokyo. Journal of the College of Science, Imperial University, 

 Toky5, Japan, vol. xviii, Art. 2. pp. 55 ; 7 plates. 1903 

 (published 8th June). 



rpHE HokkaidS forms part of the Japanese empire ; it lies to the 

 X north of the mainland, and consists chiefly of the island of Yezo 

 or Yesso, having an area about equal to that of Scotland and Wales 

 combined. The occurrence of Cretaceous Ammonites in the island 

 was first mentioned by B. S. Lyman in 1877, and his collection, 

 comprising some fifteen species of Cephalopoda, was briefly described 

 three years later by Naumann. In 1890, in his work on the fauna 

 of the Japanese Cretaceous rocks, Professor Yokohama more fully 

 described the Cretaceous Cephalopoda of the Hokkaido ; but it was 

 not until the island had been geologically surveyed by Professor 

 Jimbo and his assistants that the nature and extent of the Cretaceous 

 deposits there were known. 



The Cretaceous formation in the main island of the Hokkaido 

 rests upon Paleeozoic rocks, and is overlain by coal-bearing rocks ; 

 it extends in a north-south direction on the west side of the main 

 axis of the island ; it is a purely marine deposit, its fauna being 

 very rich in Mollusca, particularly in Cephalopoda. Although the 

 author of the present memoir went to the HokkaidS mainly for 

 the pui'pose of ascertaining the relation of the Cretaceous Ammonite- 

 bearing deposits to the coal-bearing series, he made a large collection 

 of Cretaceous fossils and carefully examined the stratigraphy of 

 the Cretaceous rocks. He proposes the following subdivisions, 

 beginning from below : — 



I. The lower Ammonite-beds with Or6^7oZma-limestone. 

 II. The ^}•^■3'o^^^a-sandstone. 



a. Lower Acanthoceras-zone or Trigonia longiloba-zone, ' 



b. Thetis-zone. 



c. Fectunculus-zone. 



III. The upper Ammonite-beds. 



a. Upper Acanthoceras-zone. 



b. Scaphites-heds. 



c. Fachydiscus-heds. 



According to the author all the beds are quite conformable to 

 each other, the upper ones passing gradually into the coal- 

 bearing series. 



Various opinions respecting the age of the Cretaceous rocks of 

 the Hokkaido have been expressed, but the author reserves the 

 discussion of the nature of the fauna until the end of his memoir. 



The whole of this part of the present memoir deals with the 

 description of those Ammonites which were formerly included in 



