284 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 



Of the Santa Cruz blocks, all except i and 3 are still intact, i has 

 been broken up completely, while of 3 a part remains intact. 



This line of evidence demonstrates clearly that of the 36 characteristic 

 species introduced by Ameghino and v. Ihering, at least 20 are to be 

 dropped; of 13 of them it has been shown (see list, p. 283) that they are 

 found anywhere within the marine series underlying the Santacruzian 

 beds, and 7 more (aside from 5 that are included in these 13) have been 

 found associated with each other in such a way in the matrix that they 

 are to be looked for at any horizon within this series. 



Of the remaining 16 species, 13 belong to the rarer forms, and, on that 

 account, are unfit to be used as characteristic fossils; the remaining 3 

 are Cttcullcea alta, Dosinia Iceviuscula and Siphonalia dilatata. These are 

 said to be Patagonian (Leonense) species, and have been found exclu- 

 sively in the neighborhood of the mouth of the Santa Cruz River. This 

 fact considering the close relations of the fauna of Santa Cruz to those 

 of other localities does not permit them to be used as characteristic fos- 

 sils for any definite horizon, but rather demonstrates that they should be 

 regarded as local elements of this particular locality (see p. 285). 



Taking together all the foregoing considerations, we arrive at the follow- 

 ing conclusions. 



// is impossible to assign according to the palczontological evidence any 

 of our Patagonian localities to any of the subdivisions distinguished by 

 Ameghino. Not only are we unable to separate the Juliense and Leonense 

 subdivisions of the ' ' Patagonian formation, ' ' biit also we are at a loss to 

 draw a line between the " Patagonian formation" and the lower, marine 

 part of the " Santacruzian formation," wliich has been called by Ameghino 

 " Piso Suprapatagonico." This conclusion is fully supported by the strati- 

 graphical observations made by Mr. Hatcher, who will elsewhere discuss 

 this question from the point of view of stratigraphy. 



The palceontological characters of the different subdivisions given by 

 Ameghino and (following him) by v. Ihering are, accordingly, of no use, 

 and have no significance at all. Patagonian and Suprapatagonian beds 

 form a palceontological unit, with one and the same fauna going througli 

 from top to bottom, without any remarkable change.^ The terms "Supra- 



1 But slight traces of a change in the fossils have been noticed ; see under Ostrea ingens and 

 Terrebratella patagonica. 



