1902.] TOX IHERIXG— MOLLUSCAN FAUNA OF PATAGONIA. 137 



Oysters," which will soon be published in the Communicaciones del 

 Miisco Nacional de Buenos Aires. Like the species of Ostrea, 

 those of Struthiolaria are also characteristic fossils of the Patagon- 

 ian and Suprapatagonian beds, which represent two different sections 

 in one great formation. 



Of great interest in this new collection are the fossils from the 

 Pyroiherium beds, collected on the Rio Chico, a tributary of the 

 Rio Chubut, and the Golfo San Jorge. Among the mollusks are 

 characteristic Gryphcea concors Ih., and G. pyrotheriorum Ih., and 

 Ostrea ameghinoi. Of species characteristic of the Patagonian 

 formation only two occur: Cardiia patagonica wSow. var., and 

 Rhynchonella plicigera Ih. Among the new species may be men- 

 tioned Bouchardia patagonica^ Turriiella 7?ialaspina, Struthiolajia 

 striatissima and Rostellaria cossmanni. The last-named species is 

 a representative of a genus which does not occur in the other 

 Patagonian Tertiary formations. In this collection there are 

 neither existing nor Mesozoic species, and I therefore believe the 

 Pyrothei'i2un beds to be Eocene, while Florentino Ameghino regards 

 them as Cretaceous. 



The general results given in my paper in the Revista do Museu 

 Paulista, Vol. II (abstract in English, p. 372 ff.), have not been 

 essentially changed, either by my later investigations or by those of 

 Dr. Ortniann. It is therefore singular that Mr. Pfeffer has, in the 

 past year, repeated his erroneous theory as to the existence of a uni- 

 form Eocene marine fauna. Even if we leave out of account the 

 Eocene formations of Patagonia, Chile and New Zealand, we must 

 consider such elementary faunistic facts as the distribution of the 

 Nummulites, which in the northern hemisphere extend from North 

 America to Europe and Asia as far as the Sunda Islands, while they 

 are wanting in the southern hemisphere. These facts cannot be 

 explained by supposed differences of temperature, but only by 

 geographical modifications, for the study of which a knowledge of 

 the Tertiary Mollusca offers one of the most important means. 



Sao Paulo, Brazil, October 28, 1901. 



