7 
190 B. N. A. BOUNDARY COMMISSION. 
above stated, they might be unhesitatingly referred to the Tertiary.* 
In 1872, Prof. Meek made a carefiil examination on the spot, of many of 
the most interesting localities in the Rocky Mountain Region, and in his 
report reaffirms and extends his former views. It would seem, however, 
that the question was approached with some ready formulated rules. He 
writes, for instance, in mentioning the reference of the fossils to the 
Cretaceous in 1871. “This I did, mainly because there were among them no 
fresh-water or strictly brackish-water types ; while up to this time we know 
of no Tertiary of marine origin in all the interior region of the Continent.’ + 
At the same time two of the shells of brackish-water aspect were referred, 
to the Eocene, though—as he himself afterward states—they were sub-. 
sequently found to have belonged to the marine beds last referred to. 
Nothing can show more clearly than this error, the delicacy of the 
investigation, even when followed on the evidence of the molluscan type 
only; or the danger of depending on the change from marine, to 
brackish, and fresh water, as a definite line. It is but fair to add, how- 
ever, that the collection including these forms was small and apparently 
in imperfect preservation. On another page, Prof. Meek says of the 
lower marine beds, represented in the Bitter Creek Series: ‘“ Although 
partly committed in favour of the opinion that this formation belongs to 
the Cretaceous, and still provisionally viewing it as probably such, I do 
not wish to disguise or conceal the fact that the evidence favouring this 
conclusion to be derived from the molluses alone, as now known, is by 
no means strong or convincing.” { The absence of all the characteristic 
Cretaceous Cephalopoda is noted as not satisfactorily explicable, and the 
decidedly Tertiary facies of the Corbule commented on. Some of the 
latter, are similar to species found in the brackish-water beds of the 
Judith River on the Upper Missouri, which have generally been regarded 
as Eocene, though now, together with the Fort Union beds, by some 
included in the Cretaceous. An Anomia, at the same time, so closely 
resembles one from the Cretaceous of Texas, that it is supposed to be 
identical with it. Directly associated with the Dinosaurian remains in 
the beds at Black Butte, is found a shell indistinguishable from Viviparus 
trochiformis, originally described from the typical Fort Union beds, near 
Fort Clarke, on the Missouri. The unity of the lignite series now 
renders itself apparent, and the impossibility of referring their eastern 



* This seems to have already occurred, as Mr. Etheridge, Pelwontologist to the Geological Survey of 
Great Britain, has referred shells obtained by Dr. Hector at the Cypress Hills,—which in all probability 
belong to this formation—to the marine Eocene. 
t U.S. Geol. Sury. Territ., 1872, p. 458. t Ibid., p. 458. 



