428 0. Meyer — Genealogy and Age of the Species 



accompanying Tuomey's geological maps of Alabama, the Ter- 

 tiary strata are represented as dipping southward, conformably 

 with those of the Cretaceous. Nevertheless, in the section from 

 Baker's Bluff to the lower salt works on the Tombigby, he 

 finds the white limestone (=Jackson and Vicksburg groups) 

 occupying 'a trough-like depression in the Buhrstone forma- 

 tion.' In conversations with me, a few months prior to his 

 death, he expressed his belief that such was the general dispo- 

 sition of the Tertiary strata, and that on close examination it 

 would turn out that the strata passed over in going southward 

 from the border of the Cretaceous, would be again passed over 

 in reversed order still farther south. My report- of the exist- 

 ence in Mississippi of a lignitiferous formation (the Grand Gulf 

 group) southward of the marine Tertiary seemed to confirm 

 this view." We see that Tuomey before his death came to the 

 same opinion about the stratigraphy of the Southern Old-ter- 

 tiary that is represented by the above profile. 



How does Hilgard now explain this "anomalous reappear- 

 ance of older strata"? He finds the cause of it in local up- 

 heavals. In reference to Jackson, he says (I, p. 129): "It 

 seems difficult to account for this condition of things unless by 

 supposing a local upheaval of the underlying formation to have 

 taken place before the deposition of the lowest of the Jackson 

 stage." In II, p. 38, he explains the other two facts in a simi- 

 lar way : " Similarly, if between Baker's Bluff and the Salt 

 Works on the Tombigby, or between Dr. Miller's and Eed 

 Bluff on the Chickasawhay, the sea bottom had a slight trough- 

 shaped undulation (such as the ocean beds of our time fre- 

 quently exhibit) the existing state of things would result."' 

 We see that Hilgard has to use the hypothesis of local undula- 

 tion in each of the three sections which are studied, and each 

 time at the southern part of the belt. This is not probable, 

 but it is possible. 



There are, however, other observations of Hilgard, which 

 agree with my cross-section, but which force him to more 

 hazardous hypotheses. As already cited, he has not observed 

 the juxtaposition of the Grand Gulf group with the marine 

 Tertiary on the Chickasawhay. He continues, however (II, p. 

 38), that, "in Hinds, Bankin and Smith counties their relative 

 age is clearly exhibited." From these words we might expect 

 that he has observed there the Grand Gulf beds overlapping the 

 marine Tertiary, especially the Yicksburgian. I cannot find 

 any place in Hilgard's publications where this is actually 

 proved. On the contrary, in the neighborhood of Brandon he 

 finds the lignito-gypseous beds of the Grand Gulf group over- 

 laid by limestone with Orbitoides (I, p. 138, II, p. 40). He 



