46 ART. 8. H. YABE. 



one, that is, Gladophlehls cfr. Dankeri.^^ As usually accepted by 

 palœophytologists, the vegetative character of the world from the 

 upper Triassic to the Wealden seems to have been remarkably 

 uniform and constant in its main features.^^ Hence it is a very 

 difficult task to make out the exact age of a given plant-bed if 

 it is ])oor in fossil contents, as in the present case. Though we 

 have now twenty-one species in all, many are not available for 

 this purpose. 



Even of specifically determinable forms, Onychiopsls elo7igata 

 seems to be of no value in settling this question, for it is a fern 

 type of decidedly east Asiatic origin, thence becoming widely 

 diffused in other lands after the Jurassic age. The fern with 

 fronds of the Cladophlebis denticidata type is not only exclusively 

 Jurassic, but is found also in the older as well as in the younger 

 strata. The two fertile pinnae which the writer has compared 

 with Coniopteris hymenophylloides, and the detached leaves of 

 Coniferae also aftbrd us no sure basis for a chronological correla- 

 tion, because a determination based on such fragments must always 

 be uncertain. Podozamites lanceolakis and equisetaceous remains 

 seem equally of little value in this respect. 



Excluding the above species and such as are new or doubt- 

 ful, there remain only five species, viz. Adiantites tSewardi, Conio- 

 pteris Heerianus, Diciyozamites falcatus, JSilssonia orienialis, and 

 Podozamitas Reinii, which are available for determining the age 

 of the strata. 



According to Mr. S. Matsushima/^ Adiantites Seivardi 

 occurs at Kinebashi, Uchinami and Otani, Onogöri, prov. Echizen, 



1) Seward: took Equisetum Ushimarcnse as a Wealden type. 



2) Sewakd : Floras of the Past : their Composition and Distribution. Pp. 13-22. 



3) Matsushima: a Geol. Rep. uf the East. Part, of Echizen etc. (MS.), p. 188. 



