268 PATAGONIAN EXPEDITIONS : PALAEONTOLOGY. 



impossible. That this is not due to defective observation, will be shown 

 further on, and it will be demonstrated, that the palaeontological charac- 

 ters given by Ameghino do not hold good in the face of a careful com- 

 parison with our material. 



Ameghino (1899) gives the following characteristic fossils for his sub- 

 divisions. 



Piso Juliense : 



Hypechinus patagonensis. Rhynchonella plicigera. 



Echinarachnius juliensis ( = Scutella pata- Bouchardia zitteli. 



gonensis). Pecten geminatus. 



Schizastcr ameghinoi. Pecten prammcius. 



Terebratula patagonica (= Terebratella p.). Siphonalia noachina. 



Piso Leonense : 



Ostrea percrassa (= 0. ingens). Turritella argentina (= T. ambulacrum). 



Perna quadrisulcata. Struthiolaria ornata. 



Cucullaa alta. 



Piso Siiprapatagonico : 



Ostrea patagonica (= 0. ingens). Amathusia angulata. 



Pecten quemadensis (= P. geminatus). Dentalium octocostatum (= D. octocostellatuni). 



Cytherea splendida (= Meretrix iheringt). Valuta ameghinoi. 



It is most important to know, where we are to look for the type-locali- 

 ties of these divisions. In this respect Ameghino is remarkably careless ; 

 indeed, he does not say in any case, what we are to take for typical rep- 

 resentations of his divisions, and thus we have to guess, or rather to infer 

 from the names given, which one is the locality intended in each case. 

 The Piso Juliense is apparently called after San Julian, and this we must 

 take for the type-locality of it (see below). The Piso Leonense has been 

 named apparently from Mt. Leon at the mouth of the Santa Cruz River, 

 and thus those beds, of which the list of fossils is given above, are to be 

 taken as representation of this division. And indeed, all five species, 

 mentioned by Ameghino as characteristic of this subdivision, have been 

 found at the mouth of the Santa Cruz River, and further, since two of 

 them, Cucullcea alta and Struthiolaria ornata, have been found nowhere 



