8 
PATAGONIAN EXPEDITIONS PALAEONTOLOGY. 
It seems probable that Steinmann’s clay-shale system includes the 
Pueyrrydon series, but of the few fossils that he cites not one is repre- 
sented in Mr. Hatcher’s collection by similar species, nor even by the 
same genus, unless it is the ammonite, which is not cited with sufficient 
definiteness to permit comparisons. 
The collections studied by Behrendsen came from a region 500 to 800 
miles north of Lake Pueyrrydon. From them he determined the pres- 
ence of several Jurassic and Cretaceous horizons, including Lias, Lower 
Oolite, Tithonian, Neocomian, Aptian (Gault), and Upper Cretaceous. 
The small number of species cited from some of the localities and horizons, 
however, must have made part of these determinations doubtful. 
At one locality on the Arroyo Pequenco, between Rio Salado and Rio 
Malargue, strata referred to the Upper Neocomian yielded only Exogyra 
couloni \ fragmentary remains of a Crustacean, a poorly preserved Trigonia 
that is compared with T aliformis , a Rliynchonella , and Mytilus cuvieri. 
The fact that some of the European forms referred to E. couloni differ 
so much from the typical form that they may be compared with Ostrea 
tar den sis, suggested that the latter may be the form referred to E. couloni 
by Behrendsen, but his description and the figures to which he especially 
refers for comparison indicate a very different form. A poorly preserved 
specimen of Trigonia subventricosa might also reasonably be compared 
with T. aliformis. There is a possibility therefore that the Pequenco 
horizon may be the same as a part of the Pueyrrydon series. 
The Aptian or Gault of Behrendsen’s paper is represented by a few 
fossils from “ Portezuelo de Carqueque,” some distance north of the last 
mentioned locality. The only forms listed from this horizon are Am- 
monites sp., Ostrea sp., Pecten sp., and Serpula phillip si Roemer, the last 
named species evidently being the basis of the determination of the age 
of the bed. The Ostrea is a mere unidentifiable fragment and the de- 
scriptive notes on the Ammonites and the Pecten make it certain that they 
can not be identical with any of the Pueyrrydon species. Serpula phil- 
lipsi , however, as described and figured from the Gault of England and 
Germany has considerable resemblance to the form I have described as 
Tubulostium pupoides , though for reasons pointed out in the description 
of the latter species it is not considered identical nor even congeneric. 
It is mentioned here merely as an example of possible identity that may 
some time be established by comparison of specimens from the two re- 
