Barrande on the Primordial Fauna and Taconic System. 213 
“Besides, all who have seriously studied paleontology know well that 
each geological epoch, or each fauna, has its proper and characteristie 
forms, which once extinct reappear no more. This is one of the great 
and beautiful results of your immense researches, which have generalized 
this law, recognized by each one of us within the limits of the strata he 
describes. 
eat American paleontologist arrived long since at the same con- 
clusion, for in 1847 he wrote the following passage in the Introduction to 
the first volume of the Monumental Work consecrated to the Palzontolo- 
performed their parts in the economy of creation, have lived their period 
and perished i 
Sauna, and giving them names the most significant of this first creation, 
he thinks it his duty to teach us that these three trilobites belong to a 
_ “In effect, according to the text of J. Hall, the three trilobites in ques- 
tion were fou 
g0 beyond indicating the horizon of certain fossils, and no one would 
think of as ing a guaranty for such indications. But on this occasion 
the great American paleontologist thinks it necessary to support his stra- 
‘pectable 
his Memo} 
the «nom In addition to the evidence heretofore possessed regarding 
of Position of the shales containing the Trilobites, I have the testimony 
of Sir W. E. Logan, that the shales of this locality are in the upper part 
ie Hudson River group, or forming a part of a series of strata which 
It 1s inclined to rank as a distinct group, above the Hudson River proper. é 
“ould be quite superfluous for me to add one word in support of the 
pg of the most able stratigraphical geologist of the. os es. 
“Now, when a savant like J. Hall thinks himself obliged to invoke 
es to guarantee the exactness of the position of a few fossils, it is 
“Sar that the determination of this position is diffienlt 
: 40 Journ Sci.—Suconp Sexizs, Vou. XXXI, No. 92.—Manox, 1861. 
28 
