[matthew] CAMBRIAN FORMATION IN EASTERN CANADA 83 



About the time of the appearance of the typical form of Acro- 

 thyra the first examples of the well-known genus Acrothele are met 

 with in the Cape Breton Cambrian. But while its presence in the 

 Etcheminian measures of Cape Breton marks the upper subfauna, 

 this genus continues to be found also in the faunas of the Paradoxides 

 beds both in this country and in Europe. 



The genus Acrotreta also appears first in the Upper Etcheminian 

 in Cape Breton, but is not confined to this group for it is a character- 

 istic fossil of the Paradoxides zone and so its presence does not define 

 the age of a set of beds with the same exactness as the little Acro- 

 thyra. We seem, therefore, to be thrown back upon this latter genus 

 as the most distinctive from of the Cape Breton Etcheminian terrane. 



Since Holasaphus, occurring in association with the Para- 

 doxides, can no longer be regarded as an Etcheminian genus, it becomes 

 necessary to remove it from an association with that terrane; hence 

 it should be removed from a page in my paper on "Geological Cycles 

 in the Maritime Provinces of Canada" where it is used as a typical 

 form of the Etchiminian terrane; therefore erase the name at page 113 

 of that article.* 



GENERAL REMARKS ON THE FAUNAS. 



It is of interest to note that in placing the Young Point fauna 

 in the Paradoxides zone several types which recall Ordovician genera 

 are found to have had an earlier origin than the Ordovician age. 



Billingsella. The resemblance to Clitambonites or B. retrofiexa 

 is such that it was once thought that the beds in which it occurs may 

 have been Ordovician. 



Holasaphus, occurring with it, has a compact head shield and has 

 a spine on the front of this shield like Magalaspis of the Ordovician 

 of northern Europe. The four other forms of Young Point resemble 

 more those of the middle Cambrian, and yet the presence of a Para- 

 doxides in company with them shows that we are dealing with one 

 of the older Cambrian faunas. 



An interesting point brought out by the study of the Cambrian 

 faunas of Cape Breton island, is that the genus Beyrichia in America 

 appeared in the Paradoxides beds ; not, however, in the lower, but in the 

 upper Paradoxides beds. 



I think that Raphistoma, whose relatives are common in Or- 

 dovician strata, was not found in Cambrian measures until it was noted 

 as occurring at Kelly's island, where it is found in sandstones of the 

 age of Division 2 of the St. John group. 



•Geol. Cycl. Marit. Prov. Can.— Trans. Ry. Soc. Can. (1908) Sec. IV, p. 133. 



