336 WALCOTT 



is the only American geologist who has held rigidly to this view : 

 or at least the only one who has contended actively against Mr. 

 Walcott's reference of this fauna to a position below that of 

 Paradoxides. 



Arguing from biologic relations, Mr. Matthew classifies the 

 Atlantic North American Cambrian as follows -} 



ATLANTIC NORTH AMERICA. 



r Dictyonema fauna. 

 Upper Cambrian... < Peltura fauna. 

 (^ Olenus fauna. 



f Paradoxides fauna. 

 Newfoundland species described 

 in this article. 

 1^ Protolenus fauna. 



In the final paper, establishing the ' Etcheminian ' as pre-Cam- 

 brian, he says, in speaking of the strata carrying the Olenellus 

 fauna at Manuels Brook : ^ 



Dana has said that " if strata should be found containing no 

 Trilobites, but only Worms, the lower types of Brachiopods, 

 Ostracods among the Crustaceans, and other inferior species, a 

 place in the Cambrian would properly be made for it."^ To 

 the author it appears that while a place might, for convenience, 

 be found in the Cambrian for such a fauna, it would not be 

 *' properly found" if we regard its biological significance. To 

 assign such a fauna to the Cambrian would be to ignore the im- 

 portance of the trilobites in distinguishing from each other the 

 several life-zones of the Cambrian system ; we would not recog- 

 nize as Cambrian a varied fauna from which the trilobites were 

 absent. 



Of the Olenellus fauna as it occurs at North Attleborough, 

 Mass., we read : 



As the trilobites all have continuous eyelobes, and the species 

 Microdiscus hellicinctiis is common to this locality and the 

 Protolenus zone in Newfoundland, it is evident that this fauna 

 is Protolenian. The group of trilobites to which the above 

 Microdiscus belongs, have a series of tubercles along the an- 



1 A New Cambrian Trilobite : Bull. Nat. Hist. Soc. New Brunswick, No. 

 XVII, 1899, p. 142. 



2 A Paleozoic Terrane Beneath the Cambrian : Annals N. Y. Acad. Sci., Vol. 

 XII, 1899, pp. 52-54. 



' Manual of Geology, 4th ed., pp. 487-488. 



