GEOLOGIC RELATIONS OF LARAMIE OF nEN\^R BASIN. 



87 



occurring in the Claggett and -hulith Kivor for- 

 mations of Montana, the Belly River of Canada, 

 the "Lower Laramie" of Carbon County, Wyo., 

 the "Laramie" of Black Buttes, Wyo., the 

 Mesaverde of Routt County, Colo., and of the 

 Grand Mesa of northwestern Colorado, the 

 Montana of the San Juan Basin, and other for- 

 mations. Prof. Henderson, in the letter above 

 mentioned, has the following to say regarding 

 two of the species: 



One of the most abundant fossils on the east side of Crow 

 Creek valley and thence well out on the divide to the east 

 for miles is Ostrea glabra, which is also abundant in the 

 Boulder district and in many places occurs in the Fox 

 Hills beds as well as low in the Laramie. Mclania wyo- 

 minc/cnsis also occurs 4 miles ea.st of Boulder, in marine 

 Fox Hills strata, though smaller than the exceedingly large 

 specimens on the east side of Crow ('reek. 



AMBER IN THE LARAMIE OF THE DENVER 

 BASIN. 



Amber in minute quantities has long been 

 known to be rather widely distributed in cer- 

 tain Upper Cretaceous strata of the eastern 

 LMted States,"" but so far as known to me it 

 appears to be of extremely rare occurrence in 

 other parts of North America. A small quan- 



" Hollick, Arthur, The occurrence and origin of amber in the eastern 

 United States; .\m. Naturalist, vol. 39, p. 137, 1905. Berry, E. W., 

 Coastal Plain amber: Torreya, vol. 7, p. 4, 1907. Knowlton, F. H., An 

 American amber-producing tree: Science, new ser., vol. 3, p. 582, 1896. 



tity from the Laramie at Marshall, Boulder 

 County, Colo., has recently been reported by 

 T. D. A. Cockerell.' Concerning it he wrote 

 as follows: 



This locality produces much of the coal used in Boulder 

 and has long been known to paleobotanists, having fur- 

 nished important materials to Lesquereux many years ago. 

 Perhaps the most interesting thing found was a small piece 

 of amber embedded in the .solid rock. It measures about 

 8 millimeters by 5.5 milhmeters and is translucent orange- 

 brown, darker than Baltic amber. It is practically insolu- 

 ble in alcohol; a small fragment left in it over night was 

 scarcely if at all diminished. In ether it eventually be- 

 comes opaque and friable. 



In a footnote Cockerell states that "since the 

 above was written we have found (luantities of 

 amber in the coal at Marshall. None of the 

 pieces is of large size." The amber was searched 

 for included insects, but so far without success. 



The well-known Baltic or typical amber is the 

 product of a coniferous tree, but coniferous 

 remains are of extremely rare occurrence in the 

 plant beds at Marshall, and it is (juite impossible 

 with the data at present available to ascertain 

 the plant that produced the amber found there. 

 As Cockrell stated, "Judging from the accom- 

 panying foliage, it is very probably not even 

 the product of a conifer." 



1 Ainber in the Laramie Cretaceous: Torreya, vol. 9, p. 140, 1909. 



