68 0. Meyer — Species in the Southern Old-tertiary. 



is generally known, that Foraminifera of the most different 

 formations often look extremely similar, and that the. genus 

 Orbitoides cannot be considered at all a "Leitfossil " for any 

 certain Tertiary formation. But it may be of interest to quote 

 what has been published about this same American Orbitoides. 

 Lyell sent it to E. Forbes and A. d'Orbigny. Forbes writes 

 to him,* June 14, 1847 : " As the subject stands at present, 

 then, we have no right to infer from the presence of an Orbi- 

 tolite, however abundant, that the stratum in which it occurs 

 belongs to one period more than another between the com- 

 mencement of the Cretaceous epoch and our times." D'Orbigny 

 writes, ibid., June 18, 1847: "... It is, in fact, of all genera, 

 that perhaps which has been most often misunderstood, and I 

 should call it the greatest culprit in geology, . . . the Orbitoides 

 are found in the Cretaceous and Tertiary formations." 



The gap between Mississippi and Florida, without the neces- 

 sary data for a mapping, is filled by Professor Heilprin by pro- 

 longing the hypothetical belts of Hilgard through the States of 

 Alabama and Georgia, till they meet the bulk of the Oligocene 

 of Florida. My studies lead me to saying, that I consider 

 Professor Heilprin's map, as far as the divisions of the Southern 

 Old-tertiary is concerned, entirely imaginary. 



Mr. Heilprin has not made himself a single observation 

 in the Southern Old-tertiary formation, but is acquainted with 

 its geology only by a somewhat superficial knowledge of a lit- 

 erature which needs much criticism. For this reason I do not 

 wish to give any further criticism of the text, but we may see 

 at least his views about that limestone, which interested us in 

 the preceding pages. We find, p. 29 : 



" 4. ' White limestone ' (Jacksonian), best exhibited at Clai- 

 borne (upper portion of bluff) and St. Stephens (lower moiety 

 of bluff), not very abundant in fossils — Pecten membranosus, P. 

 Poulsoni, Ostrea panda, Spondylus dumosus, 'Scutella 1 Lyelli, etc. 

 _50— ? feet." 



While Lyell in the year 1846 had to confess that he could 

 not find this white limestone in the upper portion of the bluff, 

 and concluded that it must have been eroded, this upper portion 

 of the bluff, according to Professor Heilprin, has become in 

 1884 typical for this limestone and best exhibits its character- 

 istic features. The specimen of Spondylus dumosus, which 

 Conrad found in 1833 in the lowest strata, must have migrated 

 upward since that time, and the other species must have come 

 from other places. They are indeed "not very abundant," for 

 I could not find a single specimen. 



Having now shown how the age of the Vicksburg and the 

 Jackson beds was determined, I give in the following pages 

 * Quart. Journ. Geol. Soc. London, iv, p. 12. 



