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SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 78 



that it contains. This is the bed whose fauna is also found in New 

 York State. The Widder beds, or the upper division, contain an 

 entirely different fauna and one that is not known elsewhere. The 

 entire section is well exposed in several ravines such as those shown 

 in figures 49 and 50, and is followed by black shales of Mississippian 

 age which contain conodonts and plant remains. These beds are 

 best exposed on the shores of Lake Huron at Kettle Point (fig. 51). 

 Included in the shale, which has a high bituminous content, are many 



^ 



Fig. 51. — Huron shales of Mississippian age, with included " cannon-ball " 

 concretions. Kettle Point, Lake Huron, Ontario, Canada. (Photograph by 

 E. R. Pohl.) 



and often large peculiar spherical concretions with a radially crystal- 

 line structure. The nucleus of these concretions is usually a single 

 plate of some armored fish of the Mississippian. In emerging from 

 the shales under the action of erosion and frost, these concretions 

 often split in half and lie about as the " kettles '' of local terminology. 

 The work in this district was aided by several amateur collectors 

 including Messrs. Charles Southworth and J. R. Kearny, who have 

 also been prevailed on to add to the Museum collections from their 

 lifelong accumulations of local collecting. 



