THE FORT <ASSIX HOCKS AND THEIR FAUNA. 



BY R. P. WHITFIELD. 



[Read before the Society December 27 , 1889, as a Supplement /n tht Memoir "» the 

 Calciferous Formation in the Champlain Valley >>y Professors Brainard and Seely.) 



About throe years ago, as was mentioned by Professor Seely, I published 

 in a Bulletin of the American Museum a series of fossils from Fori Cassia, 

 Vermont, and in that connection referred them to the horizon of the Birds- 

 eye limestone, partly on paleontological grounds, and to some extent on the 

 apparent Btratigraphical relations of the beds in which they were found. 



When the fossils came to me first, they were thought to be from the Tren- 

 ton limestone, but on a cursory examination I could find no species among 

 them which I could identify with any Trenton forms that I had ever seen. 

 After studying them, I visited Fort Cassin in company with Professors 

 Brainard and Seely. and spent about three hours at that locality. In look- 

 ing at the beds then I became convinced they could not be true Trenton; 

 also that they could not be very much lower in the series. After examining 

 the rocks at that point we visited the Maclurea l>eds Mt a locality (Apple- 

 tree point) 63 rod.- further north, and the next day another locality four 

 miles to the south. This lasl proved to be Trenton limestone, and contained 

 Trenton fossils. 



The Fort Cassin beds are characterized by a fauna consisting largely of 

 cephalopoda, with many gasteropoda and a few brachiopods. One of the 

 cephalopoda appeared to be identical with the form described by Professor 

 Hall as Orihoceras bilineaium, and referred to the Birdseye limestone. 

 The general character of these fossils appeared to be the Bame as thai of 

 those from the lower pari of the Trenton group, namely, the Black River 



or Birdseye limestone; and the character of the Lituites, ■ of which 



were, however, identical, was also \<rv similar. Th 'thocerata, other 



than 0. bilineatum, Hall, were entirely new, and the occurrence of Qompho- 



,,,<i- in these beds was a very peculiar feature, at leasl for an American 



locality, as it had not hitherto been found below the Niagara group. The 

 jteropods were as pecu liar in their character as the cephalopoda, and we 

 have a number of genera, all of which characterize the Trenton group 

 throughout, except Maclurea, and none of which had been found below the 

 Chazy limestone, except by the Canadian geologists, who referred them to 

 the Quebec group. Among these were a number of nearly identical, or 



114) 



