20 AET. 5. H. YABE. 



The consideration of the vertical range of the genus Fusu- 

 lina is also very difficult to summarize at present ; for the 

 geological age of the /i^sw/ma-limestones of various parts of the 

 world, is for most cases, still in dispute. For instance, there 

 are two different views about the age of the lower Productus- 

 liraestone of the Salt-range^^ and of the * Doliolina '-limestone of 

 the old Pacific coast ; some regard them as of the uppermost 

 Carboniferous, while others consider them as Permian. 



It is evidently misleading to consider a species of Fusulina 

 to have a much restricted vertical range : to give only one 

 instance, F. montipai^a is common in all deposits from the zone 

 of Spirifer mosquensis up to the Artinskian formation in Russia. 

 But as is usually the case, there is of course a possibility of 

 less longevity in the case of the more lately evolved forms 

 which have attained a higher complication of structure. 



The distribution of the four subgenera of Fui^ulhia in time 

 is fundamentally different from that of Orhitoides of the later 

 Cretaceous and Tertiary. In this latter genus, w^e can count 

 at present four principal suligenera, namely Orbitoide^ s.S., 

 Orthophragmma, Lepidocyclina and Miogyjosina, which appeared 

 in almost regular succession, each confining its distribution to a 

 certain geological age, for example, Orhitoides s.s. to the (^re- 

 taceous, Orthophragmina to the Eocene, Lepidocyclina to the 

 Oligocène and 31iogypsina to the INIiocene."' In the case of 

 Fusulina, such a replacement of an older type by a younger 

 seems never to have happened ; the species belonging to a 



1) Waagen: SaU-range Fossils, Geological Result. Pal. Tndica. Lapi'Auent: Note sur 

 les calcares a Protluctiis du S:ilt-range. Bull. Soc. Geol. France 1903. Tschernyschkw: 

 Die Obercarb. Brachiopotlen. Noetling : Ueber des Verlialtuiss zw. ProdiictuskalU und 

 Ceratitenschichten. There are many other works by tlie last named author on this subject. 



2] Some Italian authors deny to accept tills view of pouvillé and Sçlilumbçrger on tiie 

 geological range of the Foraminifera. 



