F. Ameghiao — Geology of Argentina. 19 



Carlos Amegliino found several deposits of the latter nature in the 

 gulf of San Jorge. All these isolated patches or deposits of the 

 Pampean horizon contain remains of extinct mammals of the same 

 genera and species as those of the Pampean Formation of the province 

 of Buenos Aires, which proves that they are of the same period. 



This similarity in the fauna of regions so far apart from south 

 to north as the provinces of Buenos Aires and Santa Fe, and of 

 southern Patagonia, demonstrates with the strongest proof that those 

 are mistaken who invoke the intervention of glacial agencies to 

 explain the accumulation of the pampean clay. It is Dr. Steinmann^ 

 who in a few words has most exaggerated the importance of the 

 glacial phenomena in this part of America, since he regards as of 

 glacial origin the deposits which are met with immediately below 

 the Pampean Formation as far as and beyond the same horizon of 

 Monte Hermoso. He does not state his reason for this, a circum- 

 stance which does not prevent many people from accepting his 

 opinion because of the authority which the writer referred to enjoys 

 in respect to geological questions. But in the present case he has 

 not studied the question, for he is not only unacquainted with the 

 deposits of Monte Hermoso, but even with the same Pampean 

 Formation of the province of Buenos Aires ; consequently, in 

 judging this question without proper data he has fallen into a 

 lamentable error. 



In all my works I have repeated, even to weariness, that absolutely 

 no trace of glacial marks is met with in the Pampean Formation — 

 that neither the fauna nor the flora indicate during any part of it the 

 existence of a climate colder than the present one. The six or seven 

 distinct mammal faunas which succeed one another from the deposit 

 of Monte Hermoso to the top of the Pampean Formation, all indicate 

 without exception a climate warmer and more uniform than the 

 present one. The remains of reptiles, the fresh-water mollusca, and 

 the numerous plant-remains obtained from the Pampean Formation, 

 lead to the same conclusion. It only I'eiuains to examine from this 

 point of view the fauna of marine mollusca of the same period. 

 With the object of supplying that deficiency I made an extensive 

 collection of marine mollusca from the Pampean Formation and sent 

 it to Dr. H. von Jhering, specialist on the subject, and this dis- 

 tinguished naturalist writes to me that almost all the species still 

 live on the shores of the south of Brazil.^ With this, the discussion 

 on this point must remain closed, for I consider it an impossibility to 

 discover positive facts in opposition to what we know up to now 



1 G. Steinmann, "A Sketch of the Geology of South America" : Amer. Nat. 

 1891, pp. 855-60. 



^ H. von Jhering, " Conchas marinas da formacjao pampeana de La Plata": 

 Eevista do Museo Paulista, vol. i, 1895, pp. 223-31. This collection consists of 

 nineteen species, all still existing on the Argentine coast except three, viz., Purpura 

 hmmastoma, Littorinajlava, and Nassa polijgona : the first does not survive to the 

 south of the Eio Grande del Sud, and the two last live in Santa Catalina, San Pablo, 

 and more to the north. This indicates that the oceanic waters of that period had 

 here a somewhat higher temperature than at present, which is in complete contra- 

 diction to the supposed glacial origin which some would attribute to the Pampean 

 Formation. 



