2o8 KNOWLTON 



correlated with the dinosaur-bearing beds at Black Buttes, Wyo- 

 ming, and both were then concluded to be of Laramie age. For 

 several years past, however, data having a distinct bearing on the 

 problem have been accumulating in adjacent and more remote areas, 

 which have indued the present writer to completely change his 

 opinion concerning the relations and age of the beds in question. 

 When the invertebrate fauna and the flora of the " Ceratops beds" are 

 compared with those of Black Buttes alone, it is true that a certain 

 degree of relationship can be established. Among the invertebrates, 

 for instance, it was shown that 9 species — 7 of which belong to Unto 

 — of the 28 species found in the "Ceratops beds," occur also at 

 Black Buttes, while of the 24 forms of plants then recognized it was 

 possible to identify only 8 specifically, one of which was from an 

 unknown locality, thus leaving less than one-third of the total num- 

 ber on which to ascertain the bearing on the question of age. Of 

 the remaining 7 species, 3 were found at Black Buttes, one in the 

 Montana at Point of Rocks, 2 in the Laramie at Golden, Colorado, 

 and one in the Raton Mountains of New Mexico, then supposed to 

 be of Laramie age but now thought to be higher. 



Of the undescribed forms I wrote at that time as follows: 



The afiinity of the undescribed forms is also quite clearly with the 

 true Laramie flora, and thus as nearly as can be made out, the plants 

 confirm the Laramie age of the Ceratops beds. 



This statement was based on tenative comparisons with beds then 

 supposed to be Laramie in age, but which subsequent investigation 

 has shown belong to higher horizons. Since the publication of the 

 above-mentioned paper the plants have been more thoroughly stud- 

 ied, with the result of increasing the number to 48 forms, as already 

 listed, though still showing a large proportion of new forms, with 

 more modern aflmities. Of the 14 species having an outside distribu- 

 tion, 9 are found in the Fort Union, 5 in the Shoshone, and 4 each 

 in the Laramie and Montana, thus slightly modifying the distribu- 

 tion as given in Brown's paper.^^ On these grounds the correlation 

 of the "Ceratops beds" with the beds at Black Buttes is no longer 

 admitted by the writer, and the Laramie age of the "Black Buttes 

 beds" is held in abeyance. 



" Bull. Am. Mus. Nat. Hist., vol. 23, 1907, p. 844. 



