212 THE CANADIAN NATURALIST. [Vol. 



VI. 



note in the preceding number of this Journal. One of them 

 was there described as a ''minute, circular species, with four 

 pairs of lateral muscular impressions and two smaller dorsal, all 

 radiating from a point near one side;" the other as "larger, 

 and like a Dlscina on the outside." The former occurs quite 

 abundantly in the Troy limestones, and is a very beautiful little 

 object. It varies in size from a mere point to a diameter of three 

 lines. Perfect specimens have a rich, polished appearance. The 

 other occurs more rarely. As might naturally be expected, these 

 rocks contain immense numbers of Ili/oUthes. Indeed, large 

 portions of the limestone are often almost wholly composed of 

 them. 



Without doubt this formation in New York will yet afford 

 many new species. ^'^ The even-bedded limestone east of Troy, to 

 which especial attention has been given, as well as portions of the 

 conglomerates, are literally loaded with fossils, and promise richly 

 to repay investigation for a long time to come. Their associated 

 slates, shales and sandstones have as yet afforded no fossils. Near 

 Lansingburgh. however, where what is at present regarded as a 

 lower member of the formation, consisting of heavy and thin-bed- 

 ded gray sandstones with interstratitied black slates, is exposed, a 

 few obscure Fucoids have been found, but these rocks have been 

 but imperfectly investigated. Neither the thickness nor precise 

 eastern limit of this formation has yet been ascertained. 



Troy, N. Y., May 24, 1871. 



* These rocks have hitherto been referred, thougli with some 

 doubt, to the Calciferous portion of the Quebec Group ; but all modern 

 investigations in our older strata have .steadily pointed to their higher 

 antiquity ; and it is simply justice to state that, by several geologists 

 besides those who have adopted Prof. Emmons' views of their age,, 

 this has long been guspected. 



