950 



NEW YORK STATE MUSEUM 



in the beds of the St John basin in New Brunswick. 1 Mr Mat- 

 thew had, in full appreciation of the importance of D. f 1 a - 

 b e 1 1 i f o r m e for the determination of the upper boundary 



of the Cambric system, searched for years for this fossil in the 

 black shales of division 3 (Bretonian) till the desired fauna was 

 found on Navy island in St John harbor. 



We learn from his important publications the interesting fact 

 that in the St John basin, Dictyonema flabelli- 

 forme is not restricted to a single zone above the trilobite 

 zone characterized by Peltura scarabaeoides, but that 

 this Upper Olenus fauna extends in the Canadian Cambric into 

 the Dictyonema zone, since its trilobites occur in lentils with 

 layers included in shales which contain the Dictyonema. Mat- 

 thew's practice has been to " regard the beds above the horizon 

 to which these trilobites, so far as known, are limited, to be the 

 true zone of Dictyonema, corresponding to the beds so desig- 

 nated in Europe, and to include the beds below, in which Lepto- 

 plastus, Sphaerophthalmus and Peltura are found, and which 

 also contain Dictyonema, as a lower zone corresponding to the 

 upper part of the Upper Olenus zone as developed in Wales and 

 Scandinavia." He obtains thus the following zones of the 

 Bretonian division of his St John group : 



a Zone of Parabolina spinulosa 



Z> Zone of Peltura scarabaeoides, contains also 

 Dictyonema flabelliforme 



c Zone of Dictyonema flabelliforme, typical 

 development of the species 



This is followed by an interruption of several hundred feet, the 

 fauna of which is not known, and then by the Lower Siluric 

 Phyllograptus shales. 



These results obtained in the St John basin are important in 

 several regards : they prove that Dictyonema flabelli- 

 forme is not everywhere restricted to a single graptolite hori- 

 zon, but may range through a considerable thickness, and that 

 its beginning falls distinctly into the hemera of the last trilobites 



1 See On a New Horizon in the St John Group, in Canadian Record of Science, 

 October 1891, p. 339-43, and Two New Cambrian Graptolites with Notes on 

 other Species of Graptolitidae of that Age, in N T . Y. Acad. Sci. Trans. Aug. 

 1895. p. 262-73, pi. 48 and 49. 



