42 OLAF HOLTEDAHL. [SEC. ARCT. EXP. FRAM 



are not so strongly expressed or invariable as is demanded of horizon 

 makers, two of the brachiopods, Leptcena rliomboidalis and Atrypa 

 reticularis are wihtout any stratigraphic value, and therefore cannot be 

 considered. Accordingly, we have only the following left for purposes of 

 correlation : 



Thecia swinderenana GOLDF. 



Cladopora rectilineata SIMPS. 



Gypidula coeymanensis prognostica SCHUCHERT. 



Spirifer vanuxemi HALL var. prognostica SCHUCHERT. 



Loxonema fitchi HALL. 



Of these Thecia swinderenana is a very widespread form, cited 

 from the Wenlock of Northern Europe and from the Niagaran of North 

 America (Michigan, Tennessee). It was found, however, by Professor 

 KLER of Christiania University occurring in the Norwegian Silurian 

 in rocks also of relatively high Ludlow age, in other words, it seems to 

 he stratigraphically no greatly restricted fossil. If we consider the other 

 four forms, we are dealing with species that as far as is vet known, 

 have a very limited vertical distribution, occurring in the horizon that is 

 the large new monograph of the Maryland Geological Survey, "The 

 Lower Devonian of Maryland" is called the Keyser member of the 

 Helderberg group of that state and which corresponds to the 

 Decker Ferry -Rondout-Manlius of New Jersey and the (Wilbur- 

 Rosendale?)-Cobleskill-Rondout-Manlius of eastern New York. 

 The three first mentioned of these four forms are very common in and 

 typical of this horizon. As mentioned in the descriptive portion of this 

 paper I have had an opportunity of comparing my Arctic specimens with 

 Maryland-specimens of three of these forms and the identifications have 

 furthermore been controlled by Professor SCHUCHERT, who knows the fauna 

 of the Keyser in detail. The occurrence of certain other of our forms 

 strongly supports this conclusion that we are dealing with an horizon 

 corresponding to those above mentioned. The Stenochisma of the Elles- 

 mereland-fauna approaches so closely to S. deckerensis WELLER, from the 

 Decker Ferry of New Jersey and the Keyser of Maryland, that I 

 simply regard it as a nothern representative of this form. The same 

 may be said of the variety of Spirifer modestus, a form belonging to 

 the most-typical Keyser-species. 



We have thus reached an important result, in being able to correlate 

 at any rate a greater part of the Series B with a well-known hori- 

 zon on the American Continent. It is not astonishing to find that only 



