STRATIGRAPHIC POSITION OF JUDITH RIVER FORMATION 645 
Species from Upper Pari of Claggett Formation 
Tancredia americana Mactra formosa 
Cardium speciosum Mactra alta 
Sphaeriola ? endotrachys Lunatia subcrassa 
Tellina equilateralis Vanikoropsis tuomeyana 
Thracia gracilis Baculites sp. 
Liopistha (Cymella) undata 
This has long been considered a typical ‘Fox Hills” fauna, and a number 
of its species do recur at the top of the marine Cretaceous immediately below 
the Laramie in Colorado and elsewhere. 
The table already given of the Fox Hills fauna lying below the 
Judith River contains a list of 18 species of which four, so far as 
the writer can learn, have not yet been found elsewhere in the Fox 
Hills. Out of the remaining 14, 10 have been collected in the 
Fox Hills beds of eastern Colorado, while 8 have been found in the 
Claggett of Stanton, which seems not only to contain a “typical 
Fox Hills” fauna but also to hold the same stratigraphic position. 
The Fox Hills beds of Canada occupy the same position also, but 
they are, according to Dawson, McConnell, and Tyrrell, so incon- 
stant that they have been considered as a whole with the Pierre 
and the two faunas have not been differentiated.t. This incon- 
stancy of the Fox Hills beds, especially so far as_ thickness 
goes, has also been everywhere noted south of the international 
boundary line, ranging from nothing (that is, in some places the 
overlying beds—Lance and Judith River—test on the Pierre shales) 
to 800 or 1,000 feet. This last is the thickness in the Denver basin 
of Colorado as given by Eldridge.2. In one place only, in Colorado, 
does it fall much below 1,000 feet. This is at Golden, where the 
thickness is only 500 feet, which Eldridge attributes to the non- 
deposition of the lower part. This thickness of 500 feet is about the 
same as noted by us in 1910 in south-central Wyoming. As to the 
shells in this Colorado section Eldridge says: 
While the invertebrate fossil remains occur throughout the entire thickness 
of the Fox Hills, there is an especially conspicuous array of characteristic forms 
at the very summit of the formation, in the uppermost layer of the capping 
sandstone, none of which is ever found above, and but few of which are met 
with in numbers below. 
¥ Contribution to Canadian Paleontology, 1, 29. 
2 Monographs U.S. Geol. Surv., XX VII (1896), 71. 3 [bid., p. 72. 
