274 Notices of Memoirs— J. C. Moherg — 



case, for instance, in Hisinger's Mineralogical Geography of 1808, 

 in Wahlenberg's book on the Formation of the Floor of Sweden 

 (1818), and in Dalman's Palmderna (1827), while in 1823 

 S. Nilsson, in dealing with the geology of Scania, speaks of the 

 'transition district' of Scania. As late as 1821 Angelin makes 

 use of the heading "Crustacea formationis transitionis " on the title- 

 page of his Palceontologia Sueoica, and even in 1884 Nathorst, 

 dealing with the geology of South Sweden, tried to reintroduce the 

 appellation ' transition system ' as a collective name for the Palaeozoic 

 strata of Sweden. 



Already in 1834 and 1835 Murchison and Sedgwick had proposed 

 the appellations Silurian and Cambrian for the formations which in 

 England come between the Old Red Sandstone and the primary rocks, 

 i.e. for strata which exactly correspond to the Palaeozoic formations 

 of Sweden. For reasons that I will enlarge on later there arose, 

 practically at once, dispute as to where the line should be drawn 

 between Cambrian and Silurian, or, in other words, about the 

 comprehensiveness of these systems in their relation to one another. 

 During the controversies that were consequently raised there poured 

 in from various quarters and to various ends new proposals for the 

 nomenclature of the strata in question. A number of these may be 

 specially named here, since they exercised a more or less considerable 

 influence on the nomenclature used in Sweden. 



As far as America is concerned, Emmons formulated his ' Taconic 

 System' in 1848; this, so far as it can really be considered in any 

 way uniform, may be said to correspond roughly to the lower series of 

 Sedgwick's Cambrian. Of more radical importance, however, was 

 Barrande's contribution to the question. In 1846 he proposed the 

 conception of 'Primordial Fauna', i.e. a fauna embracing the oldest 

 known organisms and especially characterized by trilobites with long 

 thorax and small (consisting of few segments) pygidium. Upon this 

 followed, in their proper turns, the second and the third (Silurian) faunas. 

 While in England it was considered adequate to divide the sedimentary 

 rocks in question into only two systems, Barrande divided them 

 into three sections, which proposal — especially since, following this 

 primordial fauna, analogues to Sedgwick's Lower Cambrian could 

 be pointed out in countries widely separated — gradually gained 

 ground, so that in 1878 Barrande, at the International Geological 

 Congress in Paris, called attention to the fact that Murchison himself, 

 in the last edition of his Siluria, had made use of a similar terminology, 

 in that he divided his Silurian into Primordial, Lower, and Upper 

 Silurian. 



It is clear that the Swedish geologists had, of necessity, to take up 

 a position in reference to this question of nomenclature. But the 

 choice, unless made haphazard, was no easy one. For in this case it 

 is not a question of paying exclusive regard to the priority of the 

 various appellations ; it is also of importance, among other things, 

 to investigate whether the terms proposed have a carefully fixed 

 range, and in what measure a certain classification can be said to be 

 suitable for giving us a clear and faithful picture of nature. 



Even if the appellations that have come into use for the Palseozoic 



