Reviews — Walcotfs Lower Cambrian or Olenellus Fauna. 33 



"There is not a sufficient assemblage of species found in the 

 oldest rocks in which animal life has been detected to constitute a 

 fauna that can be characterized either as distinct from the succeeding 

 fauna or as belonging to that fauna. At present the first recognized 

 fauna occurs in the lowest division of the Cambrian group. In 

 nearly all the localities where this lowest zone is recognized a 

 peculiar genus of Trilobites, Olenellus, is found ; and thus the name 

 ' Olenellus fauna ' and ' Olenellus zone,' have come into general use. 

 By the pal^ozoologist the fauna is called the Olenellus or Lower 

 Cambrian Fauna. To the geologist the series of rocks in which 

 the Olenellus fauna occurs is known as the lower division of the 

 Cambrian group or 'Olenellus zone' " (p. 515). 



In addition to a most valuable list, already referred to, of all the 

 more important books and papers relating to the subject, the author 

 gives a historical review of the work done on the rocks and fossils 

 included in the Olenellus zone, and the general results of the study 

 of the fauna by the geologist and paleontologist, or its physical 

 biological history and character as far as is known. 



The geologist considers it as found in certain rocks at a distinct 

 geologic horizon and studies its geologic relations. The palseo- 

 zoologist treats of it in its relations to the animal world, past and 

 present. 



Mr. Walcott first traces back the history of the Lower Cambrian 

 strata in America to 1818, when Prof. Amos Eaton first gave them 

 a definite position in the series of stratified rocks. Passing in 

 review the records of each writer, he shows the gradual develop- 

 ment of the history of this series of rocks and gives the ancient 

 and modern nomenclature by which it has been distinguished, and 

 the areas over which it has been observed. 



Mr. Walcott shows that the Lower Cambrian, or Olenellus fauna, 

 lived along the shores of the pre-Cambrian continent which from 

 east to west was almost co-extensive with that of the N. American 

 continent of to-day. That it has been observed in the north-west 

 at Mount Stephen, British Columbia ; at Eureka district, British 

 Nevada ; in Northern Arizona, in the Grand Caiion of the Colorado ; 

 on the western slope of the Wasatch Mountain ; on the Gallatin 

 Eiver, Montana ; on the Black Hills of Dakota ; in Wisconsin and 

 Minnesota ; on the Ozark Mountains, Southern Missouri ; and even 

 as far south as Liana County, Texas ; in Eastern Tennessee ; Eastern 

 and Northern Adirondack Mountains of New York ; and Green 

 Mountains ; North Attleborough and Braintree ; at St. John's, New 

 Brunswick, far northwards ; at I'Anse au Loup, N. side of Straits 

 of Belle Isle, Labrador ; and lastly in the extreme N.E. at Conception 

 Bay, Avalon Peninsula, Newfoundland. 



All this is graphically illustrated by a map (pi. xliv.), and by 

 very numerous sections and plates (pi. xlv.-xlvii.). 



Plate xlviii. shows in the same graphic method the extension 

 eastwards into Europe of probably the same series of unconformable 

 pre-Cambrian rocks on which the Cambrian series rest. These are 

 shown in Spain, in Wales (North and South) ; and we may now 



DECADE III. — VOL. IX. NO. I. 3 



