430 0. Meyer — Genealogy and Age of the Species 



20 feet thick, extremely rich in greensand, was passed through 

 into water-bearing sand. The friable shells brought up by the 

 auger are too much comminuted to allow of determination. 

 Whether this led to a continuation of the Shongalo deposit or 

 an independent basin or estuary ; there can be little doubt that 

 it also is of the Claiborne age." So we see that the non-marine 

 lignitiferous strata below the marine Tertiary have a thickness 

 of 418 feet beneath Jackson. Hilgard's last sentence gives us 

 his explanation of these phenomena, precisely expressed On p. 

 107: "The several marine stages are in most cases separated 

 by intervening strata of dark colored, often lignitic clays,. as 

 above mentioned ; moreover, both the base and the top of the 

 Older Tertiary are formed by strata of this character of consid- 

 erable thickness." Now it seems probable that, especially in 

 the lower part of the marine Tertiary, lignitiferous beds of 

 moderate thickness may appear between the other strata; but 

 what Hilgard advances here looks to me extremely improbable. 

 A Jacksonian of 30 feet, separated from a Claibornian, of 

 which no shell is determined, by 418 feet non-marine lignit- 

 iferous strata appears to me a hazardous hypothesis. In the 

 same way Hilgard is obliged to accept that the Yicksburgian is 

 separated from the Jacksonian below it by the same kind of 

 strata of unknown thickness. He might reply : the thickness 

 of these lignitiferous strata in Yicksburg is only 28 feet and 

 then follows a Jacksonian limestone (I, p. 141), but what frag- 

 ment of a fossil has he for such a determination of this lime- 

 stone? 



The most inexplicable of all things for Mr. Hilgard, how- 

 ever, must be and is the fact, that in his Grand Gulf formation, 

 which surpasses greatly in extent the whole marine Tertiary in 

 Mississippi, not a fragment of a marine shell has been found 

 (see I and II, pp. 40, 41). II, p. 40, says: "Neither Wailes r 

 who resided among them .... nor myself, who have delved 

 in scores of exposures, have ever found a trace of any fossil 

 whatsoever." If the Grand Gulf group originated by a rising 

 of the coast after the time of the Old-Tertiary, why has not a 

 single Miocene shell been found in this enormous "Miocene" 

 territory ? In II, p. 41, Hilgard attempts an explanation. 

 " Should the chain of the Antilles, after the close of the Eocene 

 epoch, have for some time cut off the Gulf of Mexico from the 

 Atlantic, it seems possible that the deposits of the former might 

 have changed their character to the extent required by the 

 facts observed. A strong influx of fresh water — perhaps that 

 pertaining to the Great Lignite era — from the continent might 

 for the time being have extinguished the Eocene marine fauna 

 without replacing it by another sufficiently numerous to be 



