372 



a very interesting pamphlet entitled ' Twelfth Annual Report of the 

 Regents of the University of the State of New York, 1859.' If you 

 possess this publication, you will find there, at page 59, a memoir of 

 Prof J. Hall, entitled ' Trilobites of the Shales of the Hudson River 

 Group.' This savant there describes three species under the names 

 Olenus Thompso7iij Olenus Vermontana, and Peltura {Olenus) holopyga. 

 The well-defined characters of these trilobites are described with the 

 clearness and precision to be expected from so skilful and experienced 

 a paleontologist as James Hall. 



" Although the specimens are incomplete, their primordial nature can- 

 not admit of the least doubt, when the descriptions are read, accom- 

 panied with wood engravings which the large dimensions of these three 

 species render sufiiciently exact. The first is 105 millim. long by 80 

 broad, the other two are somewhat smaller. 



" The heads of the two Oleni being deteriorated, the furrows of the 

 glabella cannot be recognized. The thorax has a common and re- 

 markable character, which consists in the greater development of the 

 third segment, the point of which is stronger and longer than in all the 

 other pleura. This is a striking resemblance 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 

 characteristics. The pygidium of 0. Thompsoni, the only one that is 

 known, shows no segmentation, and attests by its exiguity its relation 

 to a primordial trilobite. P. holopyga, by its whole appearance, resembles 

 the species of Sweden so well known by the name of P. Scarabceoides. 



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

 nized and described by J. Hall, are those of the trilobites of the primor- 

 dial fauna of Europe. This is so true, that I think I may say without 

 fear, if M. Angelin, or any other paleontologist practised in distinguish- 

 ing 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 Primordial fauna, and to place the schists 

 enclosing them in one of the formations containins: this fauna. Such 

 is my profound conviction, and I think any one who has made a serious 

 study of the trilobitic forms and of their vertical distribution in the old- 

 est formations will be of the same opinion. 



" Besides, all who have seriously studied paleontology 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 researches, which have general- 

 ized this law, recognized by each one of us within the limits of the 

 strata he describes. 



