ON SOME CRETACEOUS FOSSILS FROM SHIKOKU. 368 



of the rihs to the Jnpanese. I'ut it diifers in hnviiig n shorter shell 

 and a broad costellated area. 



Trifjonia pociUiformis occiirs sometimes in great aliiindanre, filling' 

 tlie whole rock. Tt is, however, mostly preserved as casts, and even 

 wlien tlie shell itself is loiuid, this is so firmly attaclied to the stone that 

 it is impossible to isolate it without breaking it to pieces. Further- 

 more, these casts are often so deformed that it is difficult to get 

 specimens on whicli we could found a good diagnosis. The above 

 figures'^ were taken from gv])sum pressings of an external cast of a 

 young as Avell as of a full growri specimen, wlii^'h was considered as 

 nearly perfect in slia])e. 



This species is one of the characteristic fossils of the Japanese 

 Cretaceous, being met with almost whereever the Cretaceous fossils 

 are found. In Shikoku it is to lie found at the following ])l:ices : 



Tanno in the Kntsuragawn l>asin ; Söy:nna and Okumin(^d:nii in 

 the Kyoseki liasin ; llagino in the Monobegawa lîasin (Kamigor', 

 Tosa) ; Sendachino and Mirano nenr Ochi, arid Yamanokanii (Xagano) 

 near Sakawa, botli in the Sakawa IVasin ; Obama, Vokoliata-mura, 

 Agawagori, Tosa. 



Outside of Shikoku, it occurs in the Sanchü P)asin. and in 

 Hokkaido. 



Trigonia Kikuchiana n.i^p. 

 V\. XI., Fig. 4, Ô, 6. 



Shell ovately trigonal, obli(pie, very convex, lîeaks antero- 

 mesial, ])rominent, incurved, and very slightly recur\ed. Anterior 

 margin convex, gradually passing into a less convex ventral margin 



1) The teeth which would be more or less visible in the dorsal as w<;ll as iu the poïtcrior 

 view of this and of the following species are not shown in onr figures, as these ligures were 

 f^ll drawn after gypsum pressings of external casts. 



