1898-1902. No. 28.1 THE CAMBRO-ORDOVIC1AN BEDS. 



As concerns the stratigraphic evidence of this trilobite, we see with 

 considerable certainly that we are in the middle or upper part of the 

 Cambrian, although no more exact determination is possible. 



This single find of a cambrian fossil is of extremely great interest, 

 as it is the only one hitherto known from the Arctic North American 

 Archipelago. In the coarse clastic sediments that occur commonly all 

 over the Arctic regions, above the archaBan rocks, no fossils older than 

 from the Trenton period have so far been discovered. 



Once more reverting to SCHEI. "The next member in the strati- 

 graphical order, overlying the second of the above series of conglome- 

 rates, is a bed of light greyish-white limestone, about 350 ft. thick 

 which cropped out midway up the vertical face of Gape Victoria 

 Head". 



The limestone here mentioned exhibits, in the pieces brought back, 

 a somewhat irregular appearance, some being rather dark and extremely 

 compact, others lighter and more coarsely crystalline. Especially typical 

 are the extremely frequent stylolite formations, varying from quite 

 small to 1 dm in height. As regards fossils we can commonly see 

 sections of fossil fragments, especially of orthocerites, from which fact 

 the limestone is named orthoceras-limestone by SCHEI. In addition we 

 can see some badly preserved bryozoa stems without structure. We 

 only see the central canal indicated by more coarsely crystalline calcite, 

 whilst the matrix around is very finely grained. Any systematic deter- 

 mination is out of the question. 



The only remains of organism which could supply us with any clue 

 to the geological age of this limestone, are those of certain small trilobites. 

 In spite of a very fragmentary character they are of considerable in- 

 terest. Although a study of these remains does not give us a deter- 

 mination of Ihe species, we may presume that we are dealing with 

 the transition zones between Cambrian and Ordovician. As far as can 

 be understood we have a stratigraphical equivalent to the zone which 

 is now considered as the very lowest Ordovician, and which round the 

 earth's surface in characterised by a Cambro-ordovician mixed fauna. 

 It corresponds to the Pogonip Group in Nevada, the Tremadoc in Eng- 

 land, the Ceratopyge division in Scandinavia, etc. 



In the limestone from Victoria Head we find two imperfect central 

 portions of head shields, which show an evident Cambrian character. 

 Presumably they represent Ptychoparia species. One head (pi. 4, fig. 5) 



