J. B. Hatcher — Geology of Southern Patagonia. 337 



study, often with no other remark than that they were from 

 the Patagonian beds. In this manner, for years, the fauna of 

 the Patagonian beds has been made to include everything from 

 the Upper Cretaceous deposits of the west coast to the Supra- 

 Patagonian beds, the beds in Entre Fios on the Parana and, 

 very likely, some forms from the Cape Fairweather beds of 

 Pliocene age. It is therefore not surprising, in view of this 

 unwarranted association of fossils, that the opinions of con- 

 chologists should have varied so much in regard to the age of 

 these beds. 



What is especially needed, is a complete series of the inver- 

 tebrates from the typical localities at the mouth of the Santa 

 Cruz and Desire rivers and the intervening coast, for study 

 and comparison with forms from horizons in both Europe and 

 North America, the age of which has been accurately deter- 

 mined from stratigraphical evidences. With this end in view 

 we made a small collection from near the mouth of the Santa 

 Cruz Fiver, which has been placed in the hands of Dr. A. E. 

 Ortmann, who considers them as not older than Eocene and has 

 thus far identified the following genera and species : Ostrea 

 hatcheri (Ort.) ; Cucullcea alta (Sow.) ; Pecten sp. ? ; Perna 

 sp. ? ; Area sp. ?; Limopsis insolita (Sow.); Limojpsis off. 

 araucana (Phil.) ; Cardita patagonica (Sow.) ; C. inaequatis 

 (Phil.); Venus meridionalis (Sow.); V. volkmanni (Phil.); 

 Glycimeris sp. ? ; Dentalium majus (Sow.) ? ; Trochus laevis 

 (Sow.) ; Turritella ambulacrum (Sow.) ; Turritella ajjinis 

 (Hup.) ; Crepidula gregaria (Sow.) ; Natica obtecta (Phil.) ; 

 Struthiolaria ornata (Sow.) ; Ficula Carolina (d'Orb.) ; 

 Voluta sp. ? ; Fusus darwinianus (Phil.) ; Cancer patagoni- 

 cus (Phil.). 



Incomplete as this collection doubtless is, yet it may be 

 regarded as typical of the beds in question. It is hoped that 

 we may soon be able to make more extensive collections from 

 these beds, but from the evidence already at hand there seems 

 no good reason for referring any part of the Patagonian beds 

 to a more remote age than Eocene. 



Miocene. 

 The Supra- Patagonian Beds. — After the deposition of the 

 Patagonian beds this region was for a considerable period ele- 

 vated above the level of the sea and subjected to erosion, and 

 doubtless much of the material composing the Patagonian 

 beds was then completely removed over large areas, especially 

 in what is now the interior region. This period of erosion was 

 of sufficient duration to accomplish great changes in the marine 

 fauna of the regions; for in the succeeding strata, which are 

 also of marine origin, there is almost a completely new list in 

 the species represented, while several new genera have been 



