ORTMANN : TERTIARY INVERTEBRATES. 287 



beds at Santa Cruz, and the Piso Mesopotamico is a mixture of fresh- 

 water beds of the northern and southern parts of Argentina. In the latter 

 he places the beds containing Astrapotherium, and thus we may say that 

 the sequence (beginning at the base) : Paranense, Mesopotamico, Pata- 

 gontco, is exactly the opposite of the actual conditions, and that Doering 

 in the first line is responsible for the inversion of the true succession of 

 the respective beds. 



Ameghiuo (1889) closely follows Doering, and although he introduces 

 a few changes, he perpetuates the fundamental mistake of Doering in 

 leaving the Patagonian beds at the top of the series ; and further, he adds 

 considerably to the confusion in creating, below Doering's "Patagonian 

 formation," a new formation called "Santacruzian," consisting of an 

 upper, fresh water, deposit (Piso Santacruzeno), and a lower, marine, de- 

 posit (Piso Subpatagonico), to which he assigns the respective ages of 

 Lower Eocene and " Paleocene." The former is undoubtedly identical 

 with our Santacruzian beds, while the latter (characterized according to 

 Ameghino, by the presence of the genus Baculites] is very doubtful ; 

 later, however, he changes the Subpatagonian beds into the Suprapata- 

 gonian, but it is impossible to tell what then becomes of their character- 

 istic fossil, Baculites. 



Ameghino clings very tenaciously to this division and to this determina- 

 tion of the respective ages, and it was not until Mercerat (1893) indicated- 

 the true sequence of the respective beds, that he did his "remarkable bit 

 of stratigraphic juggling" (Hatcher, 1900 a, p. 103). The result was the 

 following sequence (see Ameghino, 1894, p. 5) (beginning at the base): 

 Patagonian, S^^prapatagon^an, Santacruzian beds (see below). 



Moericke (1896, pp. 593 and 597) believes that the Patagonian formation 

 is of the same age as the "Navidad Stufe" of Steinmann, i. e., Miocene. 



Mercerat (1896-97) places the Patagonian formation partly in the 

 "Laramie," i. e., Upper Cretaceous, partly in the Eocene; the Suprapata- 

 gonian in the Upper Eocene. 1 



'Mercerat, 1896-97, p. 119. Since we shall not have occasion to refer to this article, it 

 may be well to remark that Mercerat's observations are far from clearing up the real state of 

 things in Patagonia, although he was the first to correct the principal error of Doering and 

 Ameghino. He takes considerable pains to give detailed profiles ; but these profiles, which fill 

 six plates, are entirely unintelligible, at any rate, I have not the slightest idea of what is meant 

 by the dotted lines appearing so frequently in them and resembling anticlines. 



The characteristic oysters mentioned by Mercerat on pages 106 and 119 for the different 



