on the Taconic System* 109 



"The heads of tlie two Oleni being injured, the furrows of 

 the glabella cannot be recognized . The thorax has a common 

 and remarkable character, which consists in the greater develop- 

 ment of the third segment, the point of which is stronger and 

 longer than in all the other pleura. This is a striking resem- 

 blance to the Paradoxides, the second segment of which has the 

 same peculiarity. Besides, there is an intimate relation between 

 these two primordial types, and we should not be surprised if 

 America furnished us with forms uniting most of their characte- 

 ristics. The pygidium of 0. Thompsoni^ the only one that is 

 known, shows no segmentation, and attests by its exiguity its re- 

 lation to a primordial trilobite. P. holopygay by its whole ap- 

 pearance, resembles the Swedish species so well known by the 

 name of P. scarabceoides. 



" Thus all the characters of these three trilobites, as they are 

 recognized and described by J. Hall, are those of the trilobites of 

 the primordial fauna of Europe. This is so true, that I think T 

 may say without fear, if M. Angelin, or any other palaeontologist 

 practised in distinguishing the trilobites of Scandinavia, had met 

 with these three American forms in Sweden or Norway, he would 

 not have hesitated to class them among the species of the primor- 

 dial fauna, and to place the schists enclosing them in one of the 

 formations containing this fauna. Such is my profound convic- 

 tion, and I think any one who has made a serious study of the 

 trilobitic forms and of their vertical distribution in the oldest form- 

 ations will be of the same opinion. 



" Besides, all who have seriously studied palaeontology know 

 well that each geological epoch, or each fauna, has its proper and 

 characteristic forms, which once extinct reappear no more. This 

 is one of the great and beautiful results of your immense re- 

 searches, which have generalized this law, recognized by each 

 one of us within the limits of the strata he describes. 



" The great American palaeontologist arrived long since at the 

 same conclusion, for in 1847 he wrote the following passage in the 

 Introduction to the first volume of the monumental work con- 

 secrated to the Palaeontology of New York. 



" ' Every step in this research tends to convince us that the 

 succession of strata, when clearly shown, furnishes conclusive 

 proofs of the existence of a regular sequence among the earlier 

 organisms. We are more and more able, as we advance, to ob- 

 serve that the Author of nature, though always working upon 



