. D. Walcott — Position of the Olenelhis Fauna. 33 



The slender Hyolithellus is much, like H. micans of the 

 Olenellus fauna, but, in the absence of the characteristic oper- 

 culum, it does not seem best to identify it as the same species. 



As known at present six species only pass from the Olenel- 

 lus zoue to the superjacent strata, in the Rocky Mountain 

 province. They are : Sjutorgina pannula, Acrothele suhsidua, 

 Acrotreta gemma, Scenella connula, Hyolithes Billingsi and 

 Olenoides quadriceps. Of these Acrotreta gemma extends up 

 to the Upper Cambrian zone, in Montana. 



Newfoundland. — The fauna of the Olenellus zone contains 

 but one species that ranges up into the Paradoxides zone — 

 Hyolithes princeps. Agraulos strenuus is closely allied to 

 Agraulos socialis of the Paradoxides fauna, and Platyceras 

 primcevum is very like P. minutissima of the Upper Cam-, 

 brian. 



The review of the sections shows but little specific relation- 

 ship between the two faunas, as only nine species are now 

 known to range from zone to zone. A review of the genera 

 shows a large percentage common to the two zones. Of the 

 68 genera of the Olenellus zone 47 pass up into the Middle 

 Cambrian. 



The genera confined to the Lower Cambrian, in America, 

 are : 



Leptoniitus. 



Protopharetva. 



Spirocyathus. 



Coscinocyathus. 



Ethmophylhim. 



Modioloides. 



Fordilla. 



Helenia. 



Coleoloides. 



Hyolithellus ? 



Protocaris. 



Olenellus. 



Bathynotus. 



Avalonia. 



Oryctocephalus. 



Protypns. 



Of the European genera, the following five : 



3Iickwitzia. 



Volborthella. 



Platysonites. 



Medusites ? 

 Frsena. 



are referred only to the Lower Cambrian. 



II. Relations of the Genera and Species of the Loiver and 

 Middle Cambrian. — The comparison between the two sub- 

 faunas will be made by considering the genera and species of 

 each class of the Lower Cambrian and comparing it with the 

 same class of the Middle Cambrian fauna. 



Algce. — As far as known to me, there are no true Algae in 



the rocks of the Lower Cambrian. That such forms existed, 



there can scarcely be any doubt, but after a study of all of the 



reported species, I think that they can be referred to trails of 



Am. Jour. Sci.— Third Series, Vol. XXXVIII, No. 223.— July, 1889. 

 3 



