22 A. Smith Woodward — Notes on Argentina. 



crossing and working upon those of the upper jaw. The typical and 

 only known species is C Botlii, with a laterally compi-essed rostrum. 



Hence, the new crocodilian fossils tend to increase rather than 

 diminish previous estimates of the antiquity of the red sandstones of 

 Neuquen. 



As to the PyrotJierium Formation, it would be premature to 

 discuss its wonderful mammalian fauna until the appearance of 

 Senor Ameghino's memoir which he is now preparing. I would, 

 however, urge that he should show quite clearly why Pijrotlierium 

 cannot be a close ally of the Australian Diprotodon and Notothermm 

 when he describes the fine skeleton he now possesses. It certainly 

 differs from the Proboscidea in some most fundamental characters. 



The few fish-teeth believed to have been obtained from the Pyro- 

 therinm Formation are unfortunately all marked with a query (?), 

 and were thus apparently not found in actual association with the 

 mammalian remains. But it is interesting to notice that one 

 Selachian tooth from Lake Argentina belongs to the genus Syne- 

 cJwdus, hitherto found only in the Cretaceous of Europe and New 

 Zealand ; while a number of teeth of Lamnidas from the same 

 locality cannot be distinguished from the common Lamna appendicu- 

 lata of the English Chalk, and others seem to agree equally well 

 with Odontaspis (? ScapanorhyncJins) suhidata. It may also be added 

 that two teeth found with these are of the form commonl}' named 

 " Sanrocephalus," and seem to be identical with those of the Cre- 

 taceous ganoid fish, ProtospJiyrmna. The remains of fishes met with 

 in certain deposits in regions where PyrotJierium occurs, are thus of 

 a decidedly Cretaceous aspect. 



The Patagonian Formation is obviously the means for solving the 

 age of the Santa Cruz Beds, for it seems to intrude into the midst 

 of their lower portion. Senor Ameghino, on the authority of the 

 conchologists, assigns to it a great age, believing it to be Upper 

 Cretaceous and Eocene ; and in discussing the Miocene or almost 

 Pliocene aspect of the Cetacea of this horizon, he argues that they 

 must have originated in the region of Patagonia and migrated to the 

 northern hemisphere at a later date. This may be so, but we can 

 now add that the few Selachian teeth from the same deposit are also 

 of a decidedly Pliocene or Miocene character. Carcharodon mega- 

 lodon, or teeth extremely similar to those thus named, occur in the 

 Patagonian Formation of Chubut ; so also do large teeth of Oocyrhina, 

 identical with those of the European Miocene and Pliocene Oxyrliina 

 Jia stalls — much larger than any hitherto found in a Cretaceous or 

 Eocene deposit. If their evidence be of any value, therefoi-e, we 

 must argue that not merely the Cetacea but also the fish-fauna of the 

 Miocene of the northern hemisphere originated at an earlier date 

 in the southern hemisphere. But in the present state of our geo- 

 logical knowledge it is still necessary to use the chronological terms 

 in question in a homotaxial sense, without reference to any theories 

 of migration or contemporaneity. The relative age of the mamma- 

 liferous Tertiary strata in the two hemispheres thus remains still 

 too uncertain to base upon them any of the wide generalizations 



