V. Discussion of the testimony borne by the 



Brachiopod Fauna regarding the relations of 



the Carboniferous of North-east Greenland to 



other Carboniferous formations. 



It is very difficult to estimate the value of a brachiopod as an 

 indicator of the more minute divisions of the Carboniferous and 

 Permian deposits, partly in consequence of the widely diverging 

 principles applied by palæontologists in their descriptions of fauna 

 (the reader need but be reminded of the difference in the determin- 

 ation of the species existing between Davidson and Waagen), but 

 also, in some degree, as a result of the varying opinions held with 

 regard to some of the formations now in question; we need only 

 mention, for example, the Productus limestone of Salt Range, India. 



But the determination of the age of a formation by means of 

 the brachiopod fauna is impeded to a considerable degree, by, above 

 all, the extensive vertical distribution of various elements of the 

 fauna, so that, in some cases, a purely quantitative statistic method 

 is not the correct one to be emploj'ed, but it becomes necessary to 

 attach a certain importance to the occurrence or absence of certain 

 fauna-elements or to their first appearance or their extinction for 

 the determination of the geological stage. 



The vertical extension of the Brachiopod Fauna. 



The 21 forms occurring in other localities, which has been spe- 

 cifically determined (or which have been closely compared with some 

 determined species), that have been given in the list on page 607, 

 and are divided into: 8 in the Lower group and 13 in the Upper, 

 can, as far as I am able (with the help of the literature at my dis- 

 posal) to ascertain their distribution, be placed in 5 different divis- 

 ions, viz. : 



XLIII. *ô 



