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432 FLORA OF TIIK LAKAMIE (iKOl'I'. 



ill Uie text, and wlii(;li furuisli a tlioroujiU ami complete account of the 

 invertebrate fauna of tliat group. In the "Introductory remarks" which 

 ])rece(le and the "General discussion" that follows this "Annotated 

 Catalogue," Dr. White again sets forth his views upon this great series 

 of rocks, which, however, bad undergone no change. Although he now 

 drops the term Post Cretaceous, he still regards the Laramie group "as 

 a transitional groii]) between the Cretaceous and Tertiary series, and 

 therefore as represetiting a ])eriod partaking of both the Mesozoic and 

 Cenozoic ages." In defining the grouj) anew, he says that "the 'Judith 

 River group,' 'Fort Union group,' 'Lignitic group,' 'Bitter C"eek coal 

 series,' 'Point of Kocks group,' and 'Bear Kiver estuary beds,' are all 

 parts of the great Laramie group," but that "the ' Wahsatch group,' 

 'Vermilion Creek group,' and 'Bitter Creek group' are regarded as at 

 least approximately equivalent strata, constituting the oldest member 

 of the purely fresh water Eocene Tertiary series of deposits in the West." 



The most important ()art of this pai)er is the acute and suggestive 

 geognostico biological discussion it contains respecting the origin and 

 evolution of these brackish- and fresh water invertebrate forms, but this 

 is outside of our present limits, and ueed only be referred to. 



The ai)pearance of Prof. Archibald Geikie's new Text-Book of Ge- 

 ology, containing allusions to western American deposits, called forth 

 from Dr. White a vigorous jirotest in his article ou "Late Observations 

 concerning the Molluscan Fauna, and the Geographical extent of the 

 Laramie Group," in the American Journal of Science for March, 1883, 

 in which he pronounces some of these statements erroneous, and says: 

 "I do not hesitate to assert that not one of the molluscan species men- 

 tioned in that statement was ever found in strata of the Laramie group, 

 the non-marine forms which he mentions being evidently those which 

 were discovered by Mr. Meek in an estuary deposit of true Cretaceous 

 age, at Coalville, Utah. Furthermore, not one of the numerous species 

 ^ which do characterize that group are anywhere mentioned in the book ;" 



and, referring to Mr. Stevenson's writings, he says in the same article: 

 "That any true Laramie strata ever alternate with those of the Fox 

 Hills group, or any other marine Cretaceous group, or that any true 

 marine fossils were ever collected from any strata of the Laramie group, 

 I cannot admit. I regard all such statemeuts as the result of a inisun- 

 j derstanding of the stratigraphical geology of the I'egion in which such 

 observations are said to have been made." 

 i^*^'^ ^ Having received a collection of typical Laramie fossils from the State 



o of Nuevo Leon, Mexico, Dr. White is now able to extend the southern 

 limit of the Laramie group to that point, and he states that the facts 

 "show more and more clearly the integrity of the molluscan fauna of 

 the great ancient iiitra-continental sea in which the Laramie group was 

 deposited, and its se[)arateness from the launa' of all other North Ameri- 

 can groups of strata (op. cit., p. 209)." 



The latest utterance of this protraclcd debate is that of Mr. Lesque- 



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sV 



