10 ART. 20. — M. YOKOYAMA. 



The Ammonite-bearing slate belongs to the so-called Inlcstone 

 Series which overlies the Rhsetic plant-bed of the neighboring 

 district. The series consists of thick layers of clayslates, sand- 

 stones and conglomerates which, in the upper part, contain strata 

 of schalstein and which, therefore, have been distinguished by 

 Mr. Inouye into the Upper or Schalstein-bearing Part and the 

 Lower or Non-Schalstein Part. It is in this lower part that the 

 above Ammonites occur. 



The species of Ammonites hitherto found at Nishi-Nakayama 

 and Ishimachi are as follows : 



1. Hildoceras chrysanthemum nov. sp. 



2. Hildoceras densicostalum nov. sp. 



3. Hildoceras Inouyei nov. sp. 



4. Grammoceras (?) Okadai nov. sp. 



5. Harpoceras sp. 



6. Harpoceras "sp. 



7. Cœloceras subfibulatum nov. sp. 



8. Dactylioceras helianlhoides nov. sp. 



Besides, there is an impression of a large Aegoceras-like 

 Ammonite, together with flat Mytlus-Y\ke bivalves. 



Of the eight species of Ammonites above mentioned, Hildo- 

 ceras chrysanthemum bears a close relationship to Hildoceras 

 boréale Seebach of the Upper Lias, while the two other Hildo- 

 ceras are more or less allied to the first. Of the two Harpo- 

 ceras not specifically determined, the one shows a great resem- 

 blance to Harpoceras Lythense Young also of the Upper Lias. 

 Cœloceras suhfibulatum and Dactylioceras helianlhoides resemble 

 respectively Cœloceras ßbirfatum and Dactylioceras annulatum, 

 both described by Wright from the Upper Lias of England. 

 From these facts it is clearly to be seen that we have here a 



