322 THE CANADIAN NATURALIST. [Vol. vi. 



is likewise an objection to any geological inference from the discovery 

 of a species. All we know is that they are found in Graywacke, in 

 Germany, or elsewhere, and the position of Graywacke is too dubious 

 and ubiquitous to be of any Importance in such a case. 



I regret exceedingly that I am able to give only this meagre and 

 unsatisfactory information, and also that I have not had the satisfac- 

 tion of seeing the locality. 



I shall see you in Boston next week, if I am able to go there, and 

 will there reply more fully to the other part of your letter respecting 

 N. Y. fossils. 



I have prepared nothing for our meeting, but am coming to see 

 what others do, 



I am very sincerely, yours, &c. 

 Prof C. B. Adams. James Hall." 



" [Tv.'o specimens only have been obtained of a shell, w^hich re- 

 sembles Atrypa Hemispherica, of the Clinton group"of the New- 

 York system. Prof, Hall informs me that he is disposed to assign 

 both the Clinton group and the Medina sand-stone to one geological 

 period.— C. B. A.] " 



It is evident from the above that Prof. Hall did not consider 

 the formation to belong to the Potsdam group, but rather to the 

 Medina or Clinton. In 1861, I examined the locality and pub- 

 lished the following note in the Am. Jour. Sci., 2ud series, Vol. 

 XXXII, p. 232 : 



" On tlie age of the Red Sandstone formation of Vermont. 



By E. Billings. 



" I have lately been examining a tract of the Calciferous sandrock 

 which lies on the boundary line between Canada and Vermont, on 

 Missisquoi Bay. The rock is exposed here in long parallel ridges, 

 over an area of eight or nine miles in length and from one to three in 

 width. On the east side of the exposure there is a ridge of greyish 

 sandstone which I traced south across the boundary line, after cross- 

 ing which it soon becomes mterstratified with thick beds of rock of 

 a chocolate red or brown color. It is here the typical red sandrock 

 formation of Prof. Adams. Hearing that Dr. G. M. Hall and Rev. J. 

 B. Perry of Swanton had discovered trilobites near this place, I called 

 upon them and they kindly conducted me to the locality. It is above 

 two miles south of the line and one mile or a little more east of the 

 Highgate Springs. The individual fossils are abundant in the red 

 sandstone, but I could find only two species, a small Theca and a 

 Conocephalites. Of the latter we found only the head, but the speci- 

 mens are very numerous and some of them well preserved. The 

 species resembles Bradley's C. minutus, but is a little larger, and I 

 think quite di£tinct therefrom. It is a true primordial type, and if 



