and the Taconic System* 375 



three distinct species, in place of the single one whicli is found in 

 the group No. 2. 



"The two genera, Lingula and Discina, which complete the 

 fauna of the first group, are among those which are found in 

 the primordial fauna almost everywhere that it has been observed ; 

 but here, as elsewhere, the number of species of these genera is 

 very limited. 



" With these facts before us, it would be impossible, from a pal- 

 seontological point of view, not to recognize the primordial fauna 

 in the group No. 1. It will be understood that if for the time 

 being, we neglect all other considerations, it is because strati- 

 graphy has not as yet furnished any facts which can be appealed 

 to for the solution of the question. 



" We will now compare the fossils of the 2nd group. They 

 consist of seventeen genera, of which only three are trilobites ; 

 of these two, Agnostus and Bathyurus, occur in the first group, 

 while Ckeirurus is here met with for the first time, so that the 

 crustaceans have no longer the great predominance which is ap- 

 parent in the preceding group. Besides Ckeirurus is a type 

 which has never yet been observed in any country earlier than 

 the second fauna, and the same is true of the genus Amphion^ 

 of which Mr. Billings thinks he has discovered a pygidium which 

 is figured in his memoir, although the genus is not mentioned in 

 the list which he has given. On the other hand, we know that 

 Agnostus^ although it ascends to the summit of the second fauna, 

 never goes above it, so that the crustaceans of the second group 

 taken together, represent the second fauna. 



" The cephalopods are here represented by the two genera, Or- 

 thoceras and Cyrtoceras^ furnishing together nine species, and we 

 may remark that the species of the latter genus, four in number, 

 are relatively numerous for such a horizon. Now the cephalopods, 

 which are not rare in the second fauna, have never been observed 

 in the primordial fauna. In the table which we published in 

 1859 {Bull of the Geol. Society of June^ XVI. 543), we have 

 it is true indicated, with a doubt, the presence of an Orthoceras 

 in the primordial fauna of Scandinavia. We however take ad- 

 vantage of the present occasion to correct this indication, which 

 as we have mentioned in our Parallele p. 43, was furnished by 

 Mr. Angelin. This savant, who is now with us, informs us that 

 he has lately established in the most positive manner, that the 

 orthoceratite in question really occurs in his region B C=Cerato- 



