Stromatoporoids and of Eozoon. 



455 



were seJlnientary deposits. Possibly future geologists will be 

 comparing the successions of strata in Eozoic cretaceous rocks 

 ^Yitll those of the Mesozoic cretaceous series. 



JS'ofe 6. — Amidst the hurry of preparations for my departure 

 on a fourth expedition to Porto Santo Island to work out the 

 MonticuUpora problem ah ovo, I omitted to mention that I 

 had found three Coralline algae on a block of Eozoon cana- 

 dense, viz. (1) an incrusting pluristromatic Melohesia, (2) a 

 jointed CoraUina with terete internodes^ and (3) a Penicilhis- 

 like form with broad basal internodes and elongated tufted 

 terminal internodes. I propose to name the first provisionally 

 Melohesia canadensis, the second CoraUina teretiformis , and 

 the third Eop>emciUus aurora'. We may now be certain 

 that Eozoon canadense lived in the C/oralline zone. 



1 hope that on my return in October the authorities will 

 permit me to describe and figure the members of the Eozoic 

 fauna referred to in this pnper, viz. E. canadense^ E. vesuvii, 

 E. havaricum, E. scotician, and E. erinense. 



Tiie Eozoon problem is mainly a Foraminiferal one. Some 

 of those who have attacked it have evidently had no know- 

 ledge of Foraminifera. I hope the present paper will have 

 the effect of breaking through the crust of petroiogical preju- 

 dice which for nearly fifty years has misled the scientific 

 world with regard to an important question. 



Note 7. — The difference in construction between Eozoon 

 and the Stromatoporoids is due to the laying down of a 

 secondary skeletal deposit by the former. A typical Stromato-' 

 jjora may be compared to an inverted laminated pyramid in 

 which the succeeding layers rapidly spread out widely in the 

 horizontal plane, so that the pyramid does not topple over 

 sideways. In Eozoon, on the other hand, the coils succeeding 

 the first flat disk remain small, being unable to spread out 

 owing to deposition of secondary skeleton. Soon the little 

 pile or tower of disks leans or topples over, and the disks 

 now form horizontal rouleaux of vertically arranged disks, 

 I. e. of disks standing on their edges. 



The Stromatoporoids form horizontal laminae made up of 

 disks or coils lying on their flat surfaces, and being un- 

 hampered by secondary deposits the coils may grow to a 

 very large size. The original cause of the formation of the 

 supplementary skeleton in Eozoon probably lay in the greater 

 abundance of lime-salts in certain areas of the Eozoic seas, 

 leading to deposition of thick secondary deposits outside the 

 primary shells. 



