350 REPORT ON THE STATE CABINET. 



part of the formation comes to the surface, the upper rock does not appear 

 to be developed. I am therefore induced to believe that this limestone 

 at Racine, the mass at Leclaire and extending thence into Iowa, as well 

 as the Guelph formation in Canada and the feeble representation of the 

 same in New York, are really lenticular masses of greater or less extent, 

 which have accumulated upon the unequal surface of the ocean bed in a 

 shallow sea during the latter part of the Niagara period. These isolated 

 masses of limestone have close relations with each other, while their 

 relations with the Onondaga salt group, though very intimate in the 

 single locality in Central New York, become less and less conspicuous in 

 a westerly direction. 



In the Geology of Canada, published in 1863, the Guelph limestones 

 are described as constituting a distinct formation ; but Sir. W. E. Logan 

 remarks : 



"It has already been stated that the strata seen near the mouth of the 

 Eiviere aux Sables, at Chief's Point, probably strike along the coast by Lyell 

 Island to Cape Hurd, and belong in part to the Niagara formation, whose 

 characteristic fossils are met with in several localities along the shore. These 

 strata, however, have for the most part the lithological characters of the Guelph 

 formation, and some of their undescribed species of Muechisonia have a 

 strong resemblance to others found in this series. The Pleurotomaria liuro- 

 nensis, which belongs to the Guelph rocks, occurs on Lyell Island associated 

 with Pentamerus oblongus and other characteristic Niagara species ; so that it 

 is not impossible that some of the strata along this coast may constitute a 

 passage between the Niagara and Guelph formations. 



" The Guelph formation appears to be absent from the State of New York; 

 and in Canada it probably has the form of a great lenticular mass, the limit 

 of which between Niagara and Guelph is uncertain, though it appears to extend 

 beyond Aucaster. In the other direction, it seems to thin out in Lake Hiu'on, 

 before reaching the northern peninsula of Michigan." 



I should not omit to say here, that so far as my investigations have 

 extended on the islands of Lake Huron and Lalve Michigan, with the penin- 

 sula between the latter and Green Bay, I have found the presence of the 

 lower portions of the Niagara group, with the general absence of the higher 

 beds. At the same time, along this great extent few fossils occur except 

 Pentamerus ohlongus, Halysites catenulatus, and two species of Favosites, 

 with some other corals ; and it is only on continuing the observations to 

 the southward in Wisconsin, that we find a larger number of the Niagara 

 species proper. This indication of beds of passage, pointed out by Sir 

 W. E. Logan, will, I presume, be found in all or nearly all localities 

 where a junction of the two formations can be seen. 



