360 M. YOKOYAMÂ. 



at ]e;i8t the Irigoiiia-Samlstonc i.s to be considered as conteiiiporaiieolts 

 with the Gauko-Ceiioinuiiiaii Formation of Hokkaido (Ezo). Ah-eady 

 in my paper entitled " Versteinerungen aus der japanischen Kreide," ^' 

 I have mentioned the occurrence of a scabrous Trigonia, alUed to Tr. 

 alifonnis Park., in the Cretaceous of Kagahara Avhich I considered as 

 probal)]y belonging to tlie^ame epoch as that of Hokkaido. It is this 

 same Trigonia, 7V. jiocillifonitis as I call it, which is so profusely 

 found in the soutliern Z()ne of Shiki^ku, playing so to say the role of 

 the leading fus. 'il of the Sliik()ku Cretaceous. The above view is 

 moreover justified l)y the fact tliat Mr. Jimbo has recently discovered 

 the same form of Trigonia occurring together with Ammonites in 

 the Cretaceous of Hokkaido. Whether the Izumi-Saiuhtone is also to 

 be referred to the same age is at present unsettled, as it has not yet 

 given any characteristic fossils. 



The two species of glabrous Trigoniœ also described l)elow are 

 pakeontologically very interesting. They are forms which, like some 

 Liassic specie-^, exhiljit a great external resemblance to tlie Triassic 

 genus Myophovia. Tr'ajouia Kikucltiana, whose only ally among the 

 Trigoniie is Tr. LuKioiicnsis Bum. of the Lias of En^-land and France, 

 reminds one strongly of S(jme forms of Myophoria glalnie, e.g. M. lœviga- 

 ta Alb. The otlier s]}ecies, Tr. rotandala, has no kindred form among 

 the TrigoniiL' hitherto descriljcd ; on the other hand, it has several 

 corresponding ones among the glabrous ^lyophoria', such as M. plcheja 

 Gich., M. orb:c:tI([ris Gold/., M . vuliuida Alb. In fict, this recurrence 

 of Myophoria-like Trigonite in the Japanese Cretaceous seems to con- 

 firm the view generally entertained by palaeontologists, that there is a 

 close relationship between these two genera. 



1). Palseoatoj;iMpliica, Bd. XXXVI, 18Ü0. 



