4 PALEONTOLOGY OF NEW-YORK. 



The occurrence of such vast numbers of linguloe in this rock renders 

 extremely interesting and significant the late discovery of Mr. T. Sterry 

 Hunt, that the shells of all lingulae are composed of phosphate of lime. 

 This offers an explanation of an apparent anomaly before observed in 

 regard to these shells, showing that the conditions favorable to or admit- 

 ting their existence may preclude that of other molluscs. Thus we have 

 conclusive evidence of the occurrence of lingulae in the Potsdam sand- 

 stone, often in great numbers, and extending over an area of country more 

 than one thousand miles from east to west, and from three to five hundred 

 miles from north to south ; while not a single other shell has been pu- 

 blished to the world from the same rock over this wide area. The harsh 

 arenaceous beds of this ancient sea deposit, from Canada to the Mississippi 

 river, we find, with few exceptions, nearly destitute of calcareous matter, 

 and capable only of supporting the existence of this enduring little animal, 

 covered with its phosphatic shell, itself almost as hard as the siliceous 

 grains amid which it lies entombed. 



The Potsdam sandstone, in Iowa, is often composed of roimded or oolitic 

 granules in its higher beds ; and the beds of passage to the succeeding 

 rock are frequently of such a character that we must suppose them to have 

 been largely formed from silica in solution, or from gelatinous silica. 



The investigations made in the Canadian Geological Survey show that 

 the Calciferous sandstone is, in some parts, more highly fossiliferous than 

 in any previously known localities. The new forms, however, are few, and 

 present no wide departures in type from those before recognized. The 

 Ophileta ( Euomphalus ? ) complanata is sometimes extremely abundant, 

 hundreds of individuals occurring in a single locality. 



These variations are doubtless in a great measure due to the different 

 characters assumed by the rock in different places: In the States of Wis- 

 consin and Iowa, and the Territory of Minnesota, this rock has proved 

 quite as poor in fossils as it is in the State of New- York, and has furnished 

 fewer species compared with the area of its outcrop and exposure. In that 

 part of the country, the rock is highly magnesian, and is likewise much 



