19-4 PALJEO NTOL OGYOFNEW YORK. 



corresponding in age to the formations of the Rhenish provinces of Europe, 

 and, with our present knowledge, are parallelized with the Devonian. One 

 species may be referred to the lower formation of the carboniferous system of 

 America as at present recognized. 



It is certainly surprising that no species of Hyolithes has been noticed 

 in the extensive collections made in the Niagara group of New York, Canada, 

 Wisconsin, Indiana, Illinois, Kentucky and Tennessee. Very abundant col- 

 lections have also been made in the Lower Helderberg group in New York, 

 Canada, Maryland and Tennessee, in which no species of Hyolithes has 

 occurred, except the one described by Dr. Barrett. 



In 1867 M. Barrande (Systeme Silurien du centre de la Boheme) enumerates 

 thirty-three distinct species as occurring in the Silurian formations of Bohemia ; 

 and in the palaeozoic formations of all countries, including Bohemia, he enu- 

 merates eighty-four species. Of this number, ten species occur in the first, 

 forty-two in the second, and twenty in the third fauna of the Silurian system, 

 as recognized by M. Barrande. Ten species occur in the Devonian and one in 

 the Permian. 



The contrast in the number of species found in the different horizons in all 

 other palaeozoic countries, when compared with those of the United States, is 

 very marked. While in the second fauna of European countries we have 

 more than twice as many species as in any other horizon, we have in America, 

 in the corresponding formations, but a single known species. In the third 

 fauna, which corresponds in part to our Niagara and Lower Helderberg groups, 

 we have, in all other countries, twenty species, while in America we know but 

 a single one. Regarding the Upper Helderberg, Hamilton and Chemung 

 groups, as representing the Devonian of Europe, we have four species, while 

 there are nine species, in the European formations of the same age. 



The American species, so far as known, are much restricted in their geogra- 

 phical range. Those of the Upper Helderberg are limited to two known 

 localities ; while those of the Hamilton group are confined to the central part of 

 the State of New Yorkj those of the second and third Silurian fauna? are 

 known only in the localities from which they have been described. Our 



