THE LANCE FORMATION 351 



between the flora of the Lance formation and that of the acknowledged 

 Fort Union." There was agreement, therefore, that these non-marine 

 beds immediately above the Fox Hills are Lance, or at least not older 

 than Lance. 



The contact between the Fox Hills and the Lance in this area shows 

 irregularities at some localities which have been interpreted as proof of 

 an unconformity and erosion interval. In the paper just cited Knowlton 

 publishes a statement by Calvert advocating this interpretation, and he 

 adds his own opinion concerning the magnitude of the unconformity in 

 these words: "Whether the Laramie and various post-Laramie beds were 

 deposited and later removed throughout the Dakotas, Montana, and Wyo- 

 ming is not at present known, but certain it is that the unconformity at 

 the base of the Lance formation represents the time interval during which 

 in other areas they were laid down and subsequently removed in whole or 

 in part." Presumably in this case "various post-Laramie beds" means 

 Arapahoe and Denver and the associated unconformities. My own con- 

 clusion that there was practically no hiatus here at the base of the Lance 

 and the evidence in support of that conclusion have already been cited. 



Marine member and its Cretaceous fauna. — In the summer of 1912 

 Mr. E. Russell Lloyd began the examination of the area immediately 

 north of the Standing Eock Indian reservation in the valley of Cannon- 

 ball Eiver and its tributaries. He there found marine invertebrate fossils 

 at a number of localities believed to be in the Lance formation several 

 hundred feet above its base, and these fossils were identified as belonging 

 to the Fox Hills fauna. Mr. C. J. Hares also found a few marine fossils 

 of the same character at apparently about the same horizon much farther 

 west near the headwaters of Grand Eiver. 



Mr. Lloyd's work during 1913 has multiplied the localities and greatly 

 extended the area in which this marine fauna is found, so that the known 

 localities are distributed in a belt extending from old Fort Lincoln, on 

 the Missouri, near Mandan, Korth Dakota, to Haley, ISTorth Dakota, on 

 the north fork of Grand Eiver, a distance of more than 100 miles. His 

 work has also fixed the position of the marine member in the upper part 

 of the Lance formation, as locally developed, and above the 400 feet of 

 non-marine Lance which contain Triceratops and other reptilian fossils, 

 with a flora that is said by Knowlton to be indistinguishable from the 

 Fort TJnion flora, and hence believed by him to be Eocene. 



In my opinion, the invertebrates from the marine member of the Lance 

 belong to a Cretaceous fauna. This is indicated both by their close rela- 

 tionship with the Fox Hills fauna and by the known paleogeographic 

 facts of the late Cretaceous and the Eocene. The fauna contains a num- 



